hydra-unstable: remove `ma27` from maintainer list

I'm deploying my own Hydra via flakes for a while now and while this
package actually needs more love and a few updates, I don't have the
capacity to take care of this.

pkgs/development/tools/misc/hydra/common.nix

@@ -137,6 +137,6 @@ in stdenv.mkDerivation rec {
     description = "Nix-based continuous build system";
     license = licenses.gpl3;
     platforms = platforms.linux;
-    maintainers = with maintainers; [ ma27 ];
+    maintainers = with maintainers; [ ];
   };
 }