Update google_sign_in podspec to s.dependency 'GoogleSignIn', '~> 7.1', which is the first version that has a privacy manifest. This will prevent developers from getting warnings on iOS App Store submission.

https://github.com/google/GoogleSignIn-iOS/releases/tag/7.1.0

Add Privacy Manifest (google/GoogleSignIn-iOS#382)

7.1 minimum version is iOS 10 and macOS 10.15 which is <= to the existing google_sign_in versions, so that won't be an issue.

See also #137140