Revert "Only include .po files that has a companion .aliases file"

Commit 6044c22741 wrongly assumed that a disabled .po file had a companion
.disabled file instead of an .aliases file.

Running make after "tx pull -af" generated errors which I tried to fix.  I
shouldn't have, because the Makefile did the right thing. It warned about a
missing .aliases file for a brand new translation.

So, I'm reverting the commit and use "tx pull -f" instead the next time I
need to test existing translations.

Signed-off-by: Henrik Brautaset Aronsen <subsurface@henrik.synth.no>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>