Fix the google links from the Administration section #4
Links regarding OAuth are listed in other places and do not seem to be consistent:
IIRC, the first and the third bullets are the same, meaning that the App configuration, gets the content from the homepage. For the second one, I'm not sure how we could synchronize the documentation used in the source code and the documentation published on Store. Other extensions could be in the same case.
* simplify the instructions to configure Google authentication as the first link provided already contains the information refered in the removed link.
* keep the Google documentation link only in the Admin section of the application (the homepage suggests users to visit this section)