[Flutter, 플러터]CocoaPods's specs repository is too out-of-date

 Error: CocoaPods's specs repository is too out-of-date to satisfy dependencies.
    To update the CocoaPods specs, run:
      pod repo update

해결방법

1. Go to /ios folder inside your App Package.
2. Delete Podfile.lock
3. Run pod install --repo-update
4. cd.. (Go Back to the App Package)
5. Run flutter clean
6. Rebuild and Run the App.