Second attempt to remove MO files from source distribution

Python setup seems to include MO files by default so removing
the 'recursive-include' entry from the MANIFEST.in file was
not enough

MANIFEST.in

@@ -10,3 +10,5 @@ include youtube_dl_gui/data/pixmaps/icons-license
 
 recursive-include youtube_dl_gui/data *.png *.ico
 recursive-include youtube_dl_gui/locale *.po
+
+recursive-exclude youtube_dl_gui/locale *.mo