chore(firebase_dynamic_links): update example app proving deeplink works from terminated app state

[russellwheatley]

Description

Fix dynamic links example app. This also proves that the GoogleService-Info.plist is not necessary for deeplink to resolve.

Related Issues

closes https://github.com/firebase/flutterfire/issues/9110

Checklist

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• [ ] 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 ///).
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Breaking Change

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[Lyokone]

Maybe we can add

• It needs to be run in release mode (i.e. flutter run --release) if you wish to test it from a terminated app state.
• It needs to run on an actual device. from your comment to the README?