Upgrade android_fullscreen to AGP 7.4.2 (#2094)

Where AGP == Android Gradle plugin

Upgrade carried out by Android Studio upgrade wizard

## Pre-launch Checklist

- [x] I read the [Flutter Style Guide] _recently_, and have followed its
advice.
- [x] I signed the [CLA].
- [x] I read the [Contributors Guide].
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] All existing and new tests are passing.

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[Flutter Style Guide]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo
[CLA]: https://cla.developers.google.com/
[Discord]: https://github.com/flutter/flutter/wiki/Chat
[Contributors Guide]:
https://github.com/flutter/samples/blob/main/CONTRIBUTING.md

add_to_app/fullscreen/android_fullscreen/app/build.gradle

@@ -23,6 +23,7 @@ android {
         sourceCompatibility 1.8
         targetCompatibility 1.8
     }
+    namespace 'dev.flutter.example.androidfullscreen'
 }
 
 dependencies {