gettext: Remove variables hooks on module unload

gettext: Remove variables hooks on module unload

The gettext module does not entirely cleanup after itself in
its GRUB_MOD_FINI() leaving a few variables hooks in place.
It is not possible to unload gettext module because normal
module depends on it. Though fix the issues for completeness.

Fixes: CVE-2025-0622
Reported-by: B Horn <b@horn.uk>
Signed-off-by: B Horn <b@horn.uk>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Gbp-Pq: Topic cve-2025-jan
Gbp-Pq: Name gettext-Remove-variables-hooks-on-module-unload.patch