Remove myself from maintainers

I don't want to maintain go packages anymore because packaging is such a
PITA for go packages.

pkgs/applications/misc/madonctl/default.nix

···
     homepage = https://github.com/McKael/madonctl;
     license = licenses.mit;
     platforms = platforms.unix;
-    maintainers = with maintainers; [ matthiasbeyer ];
+    maintainers = with maintainers; [ ];
   };
 }