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 language Spanish as
well as US English in.

Change-Id: I1c45fb62bd2bd25fc2b0188be8f9d6903e743851
Closes-Bug: #1317794
Merge "Remove all mostly untranslated PO files"