chore(deps): update actions/checkout action to v3 (#349)

Source-Link: googleapis/synthtool@ca87909
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:6162c384d685c5fe22521d3f37f6fc732bf99a085f6d47b677dbcae97fc21392

Author: gcf-owl-bot[bot]

.github/.OwlBot.lock.yaml

@@ -13,4 +13,4 @@
 # limitations under the License.
 docker:
   image: gcr.io/cloud-devrel-public-resources/owlbot-python:latest
-  digest: sha256:660abdf857d3ab9aabcd967c163c70e657fcc5653595c709263af5f3fa23ef67
+  digest: sha256:6162c384d685c5fe22521d3f37f6fc732bf99a085f6d47b677dbcae97fc21392

.github/workflows/docs.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Checkout
-      uses: actions/checkout@v2
+      uses: actions/checkout@v3
     - name: Setup Python
       uses: actions/setup-python@v3
       with:
@@ -24,7 +24,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Checkout
-      uses: actions/checkout@v2
+      uses: actions/checkout@v3
     - name: Setup Python
       uses: actions/setup-python@v3
       with:

.github/workflows/lint.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Checkout
-      uses: actions/checkout@v2
+      uses: actions/checkout@v3
     - name: Setup Python
       uses: actions/setup-python@v3
       with: