chore(deps): bump google-api-python-client in /gmail/quickstart

Bumps [google-api-python-client](https://github.com/googleapis/google-api-python-client) from 1.7.8 to 2.135.0.
- [Release notes](https://github.com/googleapis/google-api-python-client/releases)
- [Commits](googleapis/google-api-python-client@v1.7.8...v2.135.0)

---
updated-dependencies:
- dependency-name: google-api-python-client
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

gmail/quickstart/requirements.txt

@@ -1,3 +1,3 @@
-google-api-python-client==1.7.8
+google-api-python-client==2.135.0
 google-auth-httplib2==0.0.3
 google-auth-oauthlib==0.4.0