Fix Jenkins translation jobs

The -propose-translation-update and -upstream-translation-update
jobs do not update from transifex since our po files contain
duplicate entries where obsolete entries duplicate normal entries.

Remove all obsolete entries to fix the jobs.

Change-Id: I1ab0f23f5b1dc9a88636dab09fadb5d44008cf51
Closes-Bug: #1299349
Merge "Fix Jenkins translation jobs" into milestone-proposed