Update google-auth requirement from ~=2.14.0 to ~=2.15.0

Updates the requirements on [google-auth](https://github.com/googleapis/google-auth-library-python) to permit the latest version.
- [Release notes](https://github.com/googleapis/google-auth-library-python/releases)
- [Changelog](https://github.com/googleapis/google-auth-library-python/blob/main/CHANGELOG.md)
- [Commits](googleapis/google-auth-library-python@v2.14.0...v2.15.0)

---
updated-dependencies:
- dependency-name: google-auth
  dependency-type: direct:production
...

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

requirements.txt

@@ -41,7 +41,7 @@ fastjsonschema~=2.16.2
 fonttools~=4.38.0
 future==0.18.2
 google-api-core~=2.11.0
-google-auth~=2.14.0
+google-auth~=2.15.0
 googleapis-common-protos~=1.57.0
 h5netcdf~=1.1.0
 h5py~=3.7.0