Remove stray header from [[Translating:Group statistics]]

Make tail cut one line more from the output sent to wiki.
<https://translatewiki.net/wiki/Thread:Translating_talk:Group_statistics/About_column_header_%22All_Flagged_Revs_messages%22>

Change-Id: I83b4240c9e44b3d4b91912da6a4d96266699819a