polyml: updated maintainers

I am not sure if we still need the old packages, nothing explicitly
depends on polyml56 or polyml57 according to a grep, not sure if
external packages might (hol and isabelle depend on polyml, the latest
version).

pkgs/development/compilers/polyml/5.7.nix

@@ -35,6 +35,6 @@ stdenv.mkDerivation rec {
     homepage = https://www.polyml.org/;
     license = licenses.lgpl21;
     platforms = with platforms; (linux ++ darwin);
-    maintainers = with maintainers; [ maggesi yurrriq ];
+    maintainers = with maintainers; [ maggesi ];
   };
 }

pkgs/development/compilers/polyml/default.nix

@@ -41,6 +41,6 @@ stdenv.mkDerivation rec {
     homepage = https://www.polyml.org/;
     license = licenses.lgpl21;
     platforms = with platforms; (linux ++ darwin);
-    maintainers = with maintainers; [ maggesi yurrriq ];
+    maintainers = with maintainers; [ maggesi kovirobi ];
   };
 }