Add message for 1.22 now that it is in Special:ExtensionDistributor

https://git.wikimedia.org/commitdiff/operations%2Fmediawiki-config/2744810e35b3cd8da15a52822d6db2855460772d

PS2: Comment added

Change-Id: I07d72af5f75b02046ed88a1f368b461afc489e6d