update the part to Google+ API
What does this MR do?
Our docs mention the following path to enable Google+ API:
From the Dashboard select ENABLE APIS AND SERVICES > Compute > Google+ API > Enable
but in fact it is:
ENABLE APIS AND SERVICES > Social > Google+ API > Enable
Reference: https://console.cloud.google.com/apis/library/plus.googleapis.com
This MR is created to update this information in the docs.