mailmap: modify the entry for Mathieu Othacehe

mailmap: modify the entry for Mathieu Othacehe

Set my gnu address as the main one.

Link: https://lkml.kernel.org/r/20241217100924.7821-1-othacehe@gnu.org
Signed-off-by: Mathieu Othacehe <othacehe@gnu.org>
Cc: Alex Elder <elder@kernel.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Geliang Tang <geliang@kernel.org>
Cc: Kees Cook <kees@kernel.org>
Cc: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Cc: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Cc: Quentin Monnet <qmo@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>