Bump google-api-core from 2.19.0 to 2.21.0

Bumps [google-api-core](https://github.com/googleapis/python-api-core) from 2.19.0 to 2.21.0.
- [Release notes](https://github.com/googleapis/python-api-core/releases)
- [Changelog](https://github.com/googleapis/python-api-core/blob/main/CHANGELOG.md)
- [Commits](googleapis/python-api-core@v2.19.0...v2.21.0)

---
updated-dependencies:
- dependency-name: google-api-core
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

requirements.txt

@@ -3,7 +3,7 @@ uvicorn==0.29.0
 starlette-prometheus==0.9.0
 google-analytics-admin==0.22.7
 google-analytics-data==0.18.8
-google-api-core==2.19.0
+google-api-core==2.21.0
 google-api-python-client==2.130.0
 google-auth==2.29.0
 google-auth-httplib2==0.2.0