MAINTAINERS: Drop Andreas as Cocoa maintainer

Peter has taken over Cocoa maintainership.
Signed-off-by: NAndreas Färber <andreas.faerber@web.de>

MAINTAINERS

@@ -1105,7 +1105,6 @@ F: ui/
 F: include/ui/
 
 Cocoa graphics
-M: Andreas Färber <andreas.faerber@web.de>
 M: Peter Maydell <peter.maydell@linaro.org>
 S: Odd Fixes
 F: ui/cocoa.m