[extension_google_sign_in_as_googleapis_auth] Update import (#3689)

Replaces deprecated import with current version.

Author: stuartmorgan-g

packages/google_sign_in/extension_google_sign_in_as_googleapis_auth/lib/extension_google_sign_in_as_googleapis_auth.dart

@@ -6,7 +6,7 @@
 
 import 'package:meta/meta.dart';
 import 'package:google_sign_in/google_sign_in.dart';
-import 'package:googleapis_auth/auth.dart' as googleapis_auth;
+import 'package:googleapis_auth/googleapis_auth.dart' as googleapis_auth;
 import 'package:http/http.dart' as http;
 
 /// Extension on [GoogleSignIn] that adds an `authenticatedClient` method.

packages/google_sign_in/extension_google_sign_in_as_googleapis_auth/test/extension_google_sign_in_as_googleapis_auth_test.dart

@@ -5,7 +5,7 @@
 // https://developers.google.com/open-source/licenses/bsd
 
 import 'package:google_sign_in/google_sign_in.dart';
-import 'package:googleapis_auth/auth.dart' as auth;
+import 'package:googleapis_auth/googleapis_auth.dart' as auth;
 import 'package:extension_google_sign_in_as_googleapis_auth/extension_google_sign_in_as_googleapis_auth.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:test/fake.dart';