Fix: remove show_group_colors from graph editor menu

The `show_group_colors` option was moved to the user preferences in
ad85256e71, but accidentally remained in the graph editor menu.

release/scripts/startup/bl_ui/space_graph.py

@@ -119,7 +119,6 @@ class GRAPH_MT_view(Menu):
         layout.prop(st, "use_realtime_update")
         layout.prop(st, "show_cursor")
         layout.prop(st, "show_sliders")
-        layout.prop(st, "show_group_colors")
         layout.prop(st, "use_auto_merge_keyframes")
 
         if st.mode != 'DRIVERS':