chore(samples): Fixed a typo in the readme

[shweta345]

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:

• Make sure to open an issue as a bug/issue before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
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Fixes #<issue_number_goes_here> 🦕

[dandhlee]

Thank you!

Commit message does not align

[dandhlee]

Ah. This has the same issue as #758.

On the commit message, it should just say chore rather than docs, as docs triggers a new release and sample updates don't need one.

Could you amend the commit message and push again? Don't need to create a new branch and a new PR, but if that helps then that works too.

[shweta345]

@dandhlee Noted. I edited the message. Can you let me know if it amended properly?

[dandhlee]

Can you amend and push? I still see it as docs: https://github.com/googleapis/python-bigtable/pull/760/commits