"Google Container Engine API" no more in docs

https://docs.gitlab.com/ee/integration/google.html#comment-3824763948

The documentation talks about 'Google Container Engine API', two issues:

1. Google+ API needs to be enabled
2. There is no longer a feature called 'Google Container Engine API' in Google's list of "features"

• From https://docs.gitlab.com/ee/integration/google.html#enabling-google-oauth, fix step 12.
• Google+ API needs to be enabled