MAINTAINERS: Add Alexandre Courbot as co-maintainer to nova-core

MAINTAINERS: Add Alexandre Courbot as co-maintainer to nova-core

Alex has extensive experience with NVIDIA GPU support, is closely
involved in nova-core development, and brings valuable Rust expertise.

In addition to his technical contributions, Alex is actively engaged with
the broader community. He works closely with contributors and
stakeholders to identify and solve issues, fosters collaboration, and
helps ensure that the Nova driver evolves in alignment with the
community.

I trust him to take a key role in making the Nova driver a successful
upstream solution for NVIDIA GPUs in the Linux kernel.

Cc: Alexandre Courbot <acourbot@nvidia.com>
Acked-by: Alexandre Courbot <acourbot@nvidia.com>
Acked-by: John Hubbard <jhubbard@nvidia.com>
Link: https://lore.kernel.org/r/20250624170517.105148-1-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>