Update FirebaseApp creation in tests

Author: kroikie

packages/cloud_firestore/test/cloud_firestore_test.dart

@@ -175,7 +175,7 @@ void main() {
     });
 
     test('settings', () async {
-      final FirebaseApp app = const FirebaseApp(name: "testApp2");
+      final FirebaseApp app = FirebaseApp(name: "testApp2");
       final Firestore firestoreWithSettings = Firestore(app: app);
       await firestoreWithSettings.settings(
         persistenceEnabled: true,

packages/cloud_functions/test/cloud_functions_test.dart

@@ -34,7 +34,7 @@ void main() {
           .getHttpsCallable(functionName: 'baz')
           .call();
       final HttpsCallable callable =
-          CloudFunctions(app: const FirebaseApp(name: '1337'), region: 'space')
+          CloudFunctions(app: FirebaseApp(name: '1337'), region: 'space')
               .getHttpsCallable(functionName: 'qux')
                 ..timeout = const Duration(days: 300);
       await callable.call(<String, dynamic>{

packages/firebase_database/test/firebase_database_test.dart

@@ -19,7 +19,7 @@ void main() {
 
     int mockHandleId = 0;
     final List<MethodCall> log = <MethodCall>[];
-    final FirebaseApp app = const FirebaseApp(
+    final FirebaseApp app = FirebaseApp(
       name: 'testApp',
     );
     final String databaseURL = 'https://fake-database-url2.firebaseio.com';

packages/firebase_storage/test/firebase_storage_test.dart

@@ -14,7 +14,7 @@ void main() {
   TestWidgetsFlutterBinding.ensureInitialized();
 
   group('FirebaseStorage', () {
-    final FirebaseApp app = const FirebaseApp(
+    final FirebaseApp app = FirebaseApp(
       name: 'testApp',
     );
     final String storageBucket = 'gs://fake-storage-bucket-url.com';