Update Android project for compatibility with Flutter 3.27

[mauriziopinotti]

Flutter 3.27 uses compileSdk 35 on Android, which requires AGP 8.1.0 or higher:

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':app:bundleReleaseResources'.
> A failure occurred while executing com.android.build.gradle.internal.res.Aapt2ProcessResourcesRunnable
   > Android resource linking failed
     aapt2 E 12-31 12:56:23 150001 150001 LoadedArsc.cpp:94] RES_TABLE_TYPE_TYPE entry offsets overlap actual entry data.
     aapt2 E 12-31 12:56:23 150001 150001 ApkAssets.cpp:149] Failed to load resources table in APK '/home/maurix/Android/Sdk/platforms/android-35/android.jar'.
     error: failed to load include path /home/maurix/Android/Sdk/platforms/android-35/android.jar.


* Try:
> Run with --stacktrace option to get the stack trace.
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* Get more help at https://help.gradle.org

BUILD FAILED in 16s
Running Gradle task 'assembleRelease'...                           17.2s

┌─ Flutter Fix ─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│ [!] Using compileSdk 35 requires Android Gradle Plugin (AGP) 8.1.0 or higher.                                                         │
│  Please upgrade to a newer AGP version. The version of AGP that your project uses is likely defined in:                               │
│ /home/maurix/Projects/simple_file_saver/simple_file_saver/example/android/settings.gradle,                                            │
│ in the 'plugins' closure (by the number following "com.android.application").                                                         │
│  Alternatively, if your project was created with an older version of the templates, it is likely                                      │
│ in the buildscript.dependencies closure of the top-level build.gradle:                                                                │
│ /home/maurix/Projects/simple_file_saver/simple_file_saver/example/android/build.gradle,                                               │
│ as the number following "com.android.tools.build:gradle:".                                                                            │
│                                                                                                                                       │
│  Finally, if you have a strong reason to avoid upgrading AGP, you can temporarily lower the compileSdk version in the following file: │
│ /home/maurix/Projects/simple_file_saver/simple_file_saver/example/android/app/build.gradle                                            │
└───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
Gradle task assembleRelease failed with exit code 1

This PR updates AGP to 8.1.4.