chore(firebase_ui_oauth_google): upgrade google_sign_in to 7.2.0

[lovelessX]

Description

Moving the google_sign_in dependency to latest (7.2.0). Note that I have not been able to get the e2e to run on my machine.

Related Issues

N/A

Checklist

Before you create this PR confirm that it meets all requirements listed below by checking the relevant checkboxes ([x]).
This will ensure a smooth and quick review process. Updating the pubspec.yaml and changelogs is not required.

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• My PR includes unit or integration tests for all changed/updated/fixed behaviors (See Contributor Guide).
• All existing and new tests are passing.
• I updated/added relevant documentation (doc comments with ///).
• The analyzer (melos run analyze) does not report any problems on my PR.
• All unit tests pass (melos run test:unit:all doesn't fail).
• I read and followed the Flutter Style Guide.
• I signed the CLA.
• I am willing to follow-up on review comments in a timely manner.

Breaking Change

Does your PR require plugin users to manually update their apps to accommodate your change?

• [] Yes, this is a breaking change.
• No, this is not a breaking change.

[gemini-code-assist]

Code Review

This pull request updates the google_sign_in dependency from ^6.2.1 to ^7.2.0 in packages/firebase_ui_auth/example/pubspec.yaml, packages/firebase_ui_oauth_google/pubspec.yaml, and tests/pubspec.yaml. There are no review comments, and I have no feedback to provide.