Don't generate `.mo` files

Since we are only using `.po` files for translation we can shave off
some setup time.

Generating the `mo` files also regenerates the PO-files, including
fuzzy translations. Those cause a lot of bugs, and we don't need them
anymore since the `po` files are generated by an external translation service.

changelogs/unreleased/bvl-dont-generate-mo.yml

+---
+title: Fix invalid fuzzy translations being generated during installation
+merge_request: 20048
+author:
+type: fixed

lib/tasks/gettext.rake

@@ -16,7 +16,6 @@ namespace :gettext do
     # See: https://gitlab.com/gitlab-org/gitlab-ce/issues/33014#note_31218998
     FileUtils.touch(File.join(Rails.root, 'locale/gitlab.pot'))
 
-    Rake::Task['gettext:pack'].invoke
     Rake::Task['gettext:po_to_json'].invoke
   end