update google-example (#277)

offline-access parameters results 400 error.

Author: hadnazzar

docs/config-examples/google.md

@@ -7,7 +7,7 @@ const config = {
   issuer: 'https://accounts.google.com',
   clientId: 'GOOGLE_OAUTH_APP_GUID.apps.googleusercontent.com',
   redirectUrl: 'com.googleusercontent.apps.GOOGLE_OAUTH_APP_GUID:/oauth2redirect/google',
-  scopes: ['openid', 'profile', 'offline_access']
+  scopes: ['openid', 'profile']
 };
 
 // Log in to get an authentication token