Fix macOS build

[nilsreichardt]

There were multiple problems:

1. Firestore iOS SDK needed be upgraded to 10.3.0 in macos/Podfile
2. google_sign_in_dartio needed to be upgraded to the latest version
3. Build Phrase script for Firebase produced an error. Therefore, I removed this build phrase script (is only needed for crashlytics). Will be fixed, when I try the alpha version of Support for multiple scheme dev, staging, prod invertase/flutterfire_cli#14

Closes #393

[github-actions]

Visit the preview URL for this PR (updated for commit 3306333):

https://sharezone-test--pr394-fix-macos-build-3-5dce53ry.web.app

_{(expires Mon, 06 Mar 2023 13:46:26 GMT)}

_{🔥 via Firebase Hosting GitHub Action 🌎}

_{Sign: 4cb3ae61e1e018abfd9841fd3239f5b49ccc034b}