package/grep: bump version to 3.12
Release notes:
https://git.savannah.gnu.org/cgit/grep.git/tree/NEWS?h=v3.12
https://savannah.gnu.org/news/?id=10753
https://lists.gnu.org/archive/html/info-gnu/2025-04/msg00008.html
Signed-off-by: Kadambini Nema <kadambini.nema@gmail.com>
Signed-off-by: Julien Olivain <ju.o@free.fr>