fix: remove unused mixin entry

Author: bconlon1

src/main/resources/cumulus_menus.mixins.json

@@ -11,7 +11,6 @@
   },
   "client": [
     "client.MusicManagerMixin",
-    "client.accessor.RealmsPlayerScreenAccessor",
     "client.accessor.ScreenAccessor",
     "client.accessor.SplashRendererAccessor",
     "client.accessor.TabButtonAccessor",