added labels api field to cloud run v2 job template

[kevingrismore]

Adds the labels field for the Cloud Run v2 API to the Cloud Run v2 worker base job template so the Labels variable in the Cloud Run v2 work pool has the intended effect.

Example

Screenshots

Checklist

• References any related issue by including "Closes #" or "Closes ".
  • If no issue exists and your change is not a small fix, please create an issue first.
• Includes tests or only affects documentation.
• Passes pre-commit checks.
  • Run pre-commit install && pre-commit run --all locally for formatting and linting.
• Includes screenshots of documentation updates.
  • Run mkdocs serve view documentation locally.
• Summarizes PR's changes in CHANGELOG.md

[desertaxle]

Thank you for your willingness to contribute to prefect-gcp! The code for this library has been moved to https://github.com/PrefectHQ/prefect/tree/main/src/integrations/prefect-gcp. Please reopen this PR there if this functionality is still needed!