The dm-devel@lists.linux.dev mailing list should only be listed under the
L: (List) tag in the MAINTAINERS file.  However, it was incorrectly listed
under both L: and M: (Maintainers) tags, which is not accurate.  Remove
the M: tag for dm-devel@lists.linux.dev in the MAINTAINERS file to reflect
the correct categorization.

Link: https://lkml.kernel.org/r/20240319181842.249547-1-visitorckw@gmail.comSigned-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Cc: Ching-Chun (Jim) Huang <jserv@ccns.ncku.edu.tw>
Cc: Matthew Sakai <msakai@redhat.com>
Cc: Michael Sclafani <dm-devel@lists.linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>