Corrected the MediaWiki 1.22 Release notes

The MediaWiki 1.22 Release notes say "THIS IS NOT A RELEASE YET", which was corrected.
The stable release version is 1.22.0, not 1.22.

Bug: 58233
Change-Id: I20e2754912b9fd76a4c57e980d5166545229c417
Merge "Corrected the MediaWiki 1.22 Release notes" into REL1_22