fix: shorebird init should not warn about missing Android project when run in a Flutter module

[eseidel]

In add-to-app example

PS C:\Users\micro\Documents\GitHub\samples\add_to_app\my_flutter_module> shorebird init
✓ Detecting product flavors (8ms)
? How should we refer to this app? (my_flutter_module) my_flutter_module
✓ Shorebird is up-to-date (0.7s)
✓ Flutter install is correct (6.4s)
✗ AndroidManifest.xml files contain INTERNET permission (2ms)
  [✗] No Android project found
1 issue detected.

🐦 Shorebird initialized successfully!

✅ A shorebird app has been created.
✅ A "shorebird.yaml" has been created.
✅ The "pubspec.yaml" has been updated to include "shorebird.yaml" as an asset.

Reference the following commands to get started:

📦 To create a new release use: "shorebird release".
🚀 To push an update use: "shorebird patch".
👀 To preview a release use: "shorebird preview".

For more information about Shorebird, visit https://shorebird.dev