Outliner Python UI cleanup: remove KEYMAPS

This was removed since 2013 (ef765b3606). It should have been removed back
then from the UI file too.

release/scripts/startup/bl_ui/space_outliner.py

@@ -87,7 +87,7 @@ class OUTLINER_MT_view(Menu):
 
         space = context.space_data
 
-        if space.display_mode not in {'DATABLOCKS', 'USER_PREFERENCES', 'KEYMAPS'}:
+        if space.display_mode not in {'DATABLOCKS', 'USER_PREFERENCES'}:
             layout.prop(space, "use_sort_alpha")
             layout.prop(space, "show_restrict_columns")
             layout.separator()