Add link to last release in hack/release_notes.sh.

[andriyDev]

fixes #11278.

Before:

$ hack/release_notes.sh
Already up to date.
Collecting pull request that were merged since the last release: v1.20.0-beta.0 (2021-04-30 23:06:50 +0000 UTC)
* site: fixed CPU benchmarking typos and small formatting [#11279](https://github.com/kubernetes/minikube/pull/11279)
* Revert "Run test2json during the test and not afterwards" [#11273](https://github.com/kubernetes/minikube/pull/11273)
* Add minikube prow testing docker image [#11251](https://github.com/kubernetes/minikube/pull/11251)
* Bump github.com/shirou/gopsutil/v3 from 3.21.3 to 3.21.4 [#11259](https://github.com/kubernetes/minikube/pull/11259)
* spelling [#11186](https://github.com/kubernetes/minikube/pull/11186)
* Output GitHub issue message to stderr [#11230](https://github.com/kubernetes/minikube/pull/11230)
* Update olm addon to v0.17.0 [#10947](https://github.com/kubernetes/minikube/pull/10947)
* ci: Make separate image for the remove functional test [#11248](https://github.com/kubernetes/minikube/pull/11248)
* Run test2json during the test and not afterwards [#11250](https://github.com/kubernetes/minikube/pull/11250)
* warn about performance for certain versions of kubernetes [#11217](https://github.com/kubernetes/minikube/pull/11217)
* Fix out stylized function formatting with an empty map instead of nothing. [#11243](https://github.com/kubernetes/minikube/pull/11243)
* Bump github.com/Azure/azure-sdk-for-go from 43.0.0+incompatible to 43.3.0+incompatible [#11261](https://github.com/kubernetes/minikube/pull/11261)
* Bump cloud.google.com/go/storage from 1.13.0 to 1.15.0 [#11263](https://github.com/kubernetes/minikube/pull/11263)
* Bump github.com/hashicorp/go-retryablehttp from 0.6.8 to 0.7.0 [#11260](https://github.com/kubernetes/minikube/pull/11260)
* update releases-beta.json to include v1.20.0-beta.0 [#11244](https://github.com/kubernetes/minikube/pull/11244)
* Fixed gsutil copy for releases-beta.json [#11245](https://github.com/kubernetes/minikube/pull/11245)
Thank you to our contributors for this release!

- Anders F Björklund
- Andriy Dzikh
- dependabot[bot]
- Ilya Zuyev
- Medya Ghazizadeh
- minikube-bot
- Sharif Elgamal
- Steven Powell
- Tomas Kral
- Yanshu
- zhangshj

After:

$ hack/release_notes.sh
Already up to date.
Collecting pull request that were merged since the last release: v1.20.0-beta.0 (2021-04-30 23:06:50 +0000 UTC)
* site: fixed CPU benchmarking typos and small formatting [#11279](https://github.com/kubernetes/minikube/pull/11279)
* Revert "Run test2json during the test and not afterwards" [#11273](https://github.com/kubernetes/minikube/pull/11273)
* Add minikube prow testing docker image [#11251](https://github.com/kubernetes/minikube/pull/11251)
* Bump github.com/shirou/gopsutil/v3 from 3.21.3 to 3.21.4 [#11259](https://github.com/kubernetes/minikube/pull/11259)
* spelling [#11186](https://github.com/kubernetes/minikube/pull/11186)
* Output GitHub issue message to stderr [#11230](https://github.com/kubernetes/minikube/pull/11230)
* Update olm addon to v0.17.0 [#10947](https://github.com/kubernetes/minikube/pull/10947)
* ci: Make separate image for the remove functional test [#11248](https://github.com/kubernetes/minikube/pull/11248)
* Run test2json during the test and not afterwards [#11250](https://github.com/kubernetes/minikube/pull/11250)
* warn about performance for certain versions of kubernetes [#11217](https://github.com/kubernetes/minikube/pull/11217)
* Fix out stylized function formatting with an empty map instead of nothing. [#11243](https://github.com/kubernetes/minikube/pull/11243)
* Bump github.com/Azure/azure-sdk-for-go from 43.0.0+incompatible to 43.3.0+incompatible [#11261](https://github.com/kubernetes/minikube/pull/11261)
* Bump cloud.google.com/go/storage from 1.13.0 to 1.15.0 [#11263](https://github.com/kubernetes/minikube/pull/11263)
* Bump github.com/hashicorp/go-retryablehttp from 0.6.8 to 0.7.0 [#11260](https://github.com/kubernetes/minikube/pull/11260)
* update releases-beta.json to include v1.20.0-beta.0 [#11244](https://github.com/kubernetes/minikube/pull/11244)
* Fixed gsutil copy for releases-beta.json [#11245](https://github.com/kubernetes/minikube/pull/11245)
Thank you to our contributors for this release!

- Anders F Björklund
- Andriy Dzikh
- dependabot[bot]
- Ilya Zuyev
- Medya Ghazizadeh
- minikube-bot
- Sharif Elgamal
- Steven Powell
- Tomas Kral
- Yanshu
- zhangshj

These release notes are relative to our [last release](https://github.com/kubernetes/minikube/releases/tag/v1.20.0-beta.0).

[k8s-ci-robot]

Hi @andriyDev. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: andriyDev
To complete the pull request process, please assign tstromberg after the PR has been reviewed.
You can assign the PR to them by writing /assign @tstromberg in a comment when ready.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
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[minikube-bot]

Can one of the admins verify this patch?

[andriyDev]

No longer relevant, it has been decided to just show a link to the full changelog.