Remove all mostly untranslated PO files

We now only import PO files that are at least 75 % translated,
so we can delete now all other PO files. The patch only
removes the mostly untranslated files. Once a file becomes mostly
translated, the bot will import it again.

This patch leaves the mostly translated languages Australian English,
US English and Brazilian Portuguese in.

Change-Id: Ib26bc5147f0dc3d49f9b97bc0b8682a8c62c81b8
Closes-Bug: #1317794
Merge "Remove all mostly untranslated PO files"