enable material m3 into google_maps example app (#1929)

google_maps/android/app/build.gradle

@@ -47,7 +47,7 @@ android {
         applicationId "com.example.google_maps_in_flutter"
         // You can update the following values to match your application needs.
         // For more information, see: https://docs.flutter.dev/deployment/android#reviewing-the-gradle-build-configuration.
-        minSdkVersion flutter.minSdkVersion
+        minSdkVersion 20
         targetSdkVersion flutter.targetSdkVersion
         versionCode flutterVersionCode.toInteger()
         versionName flutterVersionName

google_maps/android/build.gradle

@@ -26,6 +26,6 @@ subprojects {
     project.evaluationDependsOn(':app')
 }
 
-task clean(type: Delete) {
+tasks.register("clean", Delete) {
     delete rootProject.buildDir
 }