ci: Simplify flatpak job

The template has been updated to rewrite the manifest to use the
checked out tree, so it's no longer necessary to pass additional
build arguments (which are now ignored) or generate translations
before the build (it's already in the manifest).

https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1217

.gitlab-ci.yml

@@ -124,11 +124,7 @@ flatpak:
         RUNTIME_REPO: "https://nightly.gnome.org/gnome-nightly.flatpakrepo"
         FLATPAK_MODULE: "gnome-extensions-app"
         APP_ID: "org.gnome.Extensions"
-        MESON_ARGS: "$SUBPROJECT"
     extends: .flatpak
-    before_script:
-        - flatpak run --command=$SUBPROJECT/generate-translations.sh
-                      --filesystem=host org.gnome.Sdk//master
     <<: *only_default
 
 nightly: