balsa: replace romildo with timon as maintainer

pkgs/by-name/ba/balsa/package.nix

···
     mainProgram = "balsa";
     license = lib.licenses.gpl2Plus;
     platforms = lib.platforms.unix;
-    maintainers = with lib.maintainers; [ romildo ];
+    maintainers = with lib.maintainers; [ timon ];
   };
 })