temp/gnome-shell-mobile: remove dep gnome-themes-standard (MR 3587)

Follow what Alpine is doing with gnome-shell.

Fix for upstream-compat check:
  missing depend(s): gnome-themes-standard

Related: https://gitlab.alpinelinux.org/alpine/aports/-/commit/b745f99744d915c51d97bf17d8a9a4a59502a923
Related: https://gitlab.alpinelinux.org/alpine/aports/-/commit/959ad322e0cb616257443206fd3ca85f7492012d