Allow the app to compile again.

android/gradle.properties

@@ -2,6 +2,8 @@ org.gradle.jvmargs=-Xmx4G -XX:MaxMetaspaceSize=2G -XX:+HeapDumpOnOutOfMemoryErro
 android.useAndroidX=true
 android.enableJetifier=true
 # This builtInKotlin flag was added automatically by Flutter migrator
-android.builtInKotlin=false
+android.builtInKotlin=true
 # This newDsl flag was added automatically by Flutter migrator
 android.newDsl=false
+# Force the Kotlin version resolver in AGP 9 to use our target version
+kotlin.version=2.4.20