Downgrade to Gradle to 7.6.1 in mobile app

This seems to be what Flutter supports so far

https://docs.flutter.dev/release/breaking-changes/android-java-gradle-migration-guide#solution-2-manual-fix-at-the-command-line

Author: rm3l

mobile/android/gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.14.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.6.1-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists