Add punctuation to "mobile-frontend-profile-last-thank"

For consistency. Spotted by JurgenNL and reported at
https://translatewiki.net/wiki/Thread:Support/About_MediaWiki:Mobile-frontend-profile-last-thank/en

Change-Id: I6c22b33253f147064dba2e437f62ec439d1d1a45
Merge "Add punctuation to "mobile-frontend-profile-last-thank""