Strip out commented-out translations after update

This is necessary because:
- Transifex runs 'msgfmt -c' on any uploaded .po file
- pybabel adds a spurious '#~ msgid ""' to the end of some files
- 'msgfmt -c' ignores that this is commented out, and treats it
  as a syntax error (clashing with the top file definition)

i2p2www/translations/pt_BR/LC_MESSAGES/priority.po

@@ -2755,6 +2755,3 @@ msgstr ""
 msgid "Very Old Stuff"
 msgstr "Velharias"
 
-#~ msgid "Help channel"
-#~ msgstr "Canal de ajuda"
-