Drop Special:MyLanguage from wiki page group descriptions

Links to the translated version need to be added in a
different way, if neeeded.

While at it, make sure we are not trying to display
images or categorize the pages.

Bug: 47185
Change-Id: I8ac0e24058293b9bd9eb6203e081dc9b3d713f53
Merge "Drop Special:MyLanguage from wiki page group descriptions"