Bump google-api-core from 2.5.0 to 2.6.0 (#149)

Bumps [google-api-core](https://github.com/googleapis/python-api-core) from 2.5.0 to 2.6.0.
- [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@v2.5.0...v2.6.0)

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

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

requirements.txt

@@ -2,7 +2,7 @@ cachetools==5.0.0
 certifi==2021.10.8
 charset-normalizer==2.0.12
 gbq==0.5.0
-google-api-core==2.5.0
+google-api-core==2.6.0
 google-auth==2.6.0
 google-cloud-bigquery==2.34.1
 google-cloud-core==2.2.2