Changing my email address in CREDITS to be consistent with what's in use
in MAINTAINERS and mailmap. Also removed extra date information from the
CREDITS entry since I'm a maintainer for MPTCP again.

Signed-off-by: Mat Martineau <martineau@kernel.org>
Link: https://lore.kernel.org/r/20230502000545.2899055-1-martineau@kernel.org


Signed-off-by: Jonathan Corbet <corbet@lwn.net>