MAINTAINERS: Update git entry for nouveau

The gitlab repository previously associated with
the nouveau module has fallen out of use. The
drm-misc tree here:

https://gitlab.freedesktop.org/drm/misc/kernel.git



Is now where most nouveau-related patches are
applied. This change updates the MAINTAINERS file
to reflect this.

Signed-off-by: James Jones <jajones@nvidia.com>
Link: https://lore.kernel.org/r/20250826195716.1897-1-jajones@nvidia.com


Signed-off-by: Danilo Krummrich <dakr@kernel.org>