Remove @metalmatze as maintainer (#23612)

It's time. I haven't been active in years.

MAINTAINERS

@@ -5,7 +5,6 @@ Kees de Vries <bouwko@gmail.com> (@Bwko)
 Kim Carlbäcker <kim.carlbacker@gmail.com> (@bkcsoft)
 LefsFlare <nobody@nobody.tld> (@LefsFlarey)
 Lunny Xiao <xiaolunwen@gmail.com> (@lunny)
-Matthias Loibl <mail@matthiasloibl.com> (@metalmatze)
 Rachid Zarouali <nobody@nobody.tld> (@xinity)
 Rémy Boulanouar <admin@dblk.org> (@DblK)
 Sandro Santilli <strk@kbt.io> (@strk)