Update readme following move to GitLab

README.md

 # CiviCRM user guide
 
-**From the 1st September 2020 the canonical home for this repository will move to https://lab.civicrm.org/documentation/docs/user-en this repository will then function as a copy.**
+**From the 1st September 2020 the canonical home for this repository has moved to GitLab (https://lab.civicrm.org/documentation/docs/user-en). The GitHub repository has been archived.**
 
 A documentation guide for people who use [CiviCRM](https://www.civicrm.org).