Upgrade Google+ integration help page

[Claudio]

One important step missing in the help page (https://xenforo.com/help/google-integration/) is define the Consent Screen in APIs & auth.

It is a mandatory step so it shouldn't be omitted or added as extra information like now:

To change the values displayed when a user attempts to register via Google, you can customize this in your Google project via APIs & Auth > Consent screen.

This should be added to step 3 before copy the Client ID, Client secret and ask the user to test the integration