UI Cleanup: Mask keymap shouldn't be part of Clip Editor keymap

Also removed unrelated comment (copied & pasted from a few lines above I guess).
Shouldn't break any custom key configs.

release/scripts/modules/bpy_extras/keyconfig_utils.py

@@ -122,9 +122,10 @@ KM_HIERARCHY = [
         ('Clip Editor', 'CLIP_EDITOR', 'WINDOW', []),
         ('Clip Graph Editor', 'CLIP_EDITOR', 'WINDOW', []),
         ('Clip Dopesheet Editor', 'CLIP_EDITOR', 'WINDOW', []),
-        ('Mask Editing', 'EMPTY', 'WINDOW', []),  # image (reverse order, UVEdit before Image
         ]),
 
+    ('Mask Editing', 'EMPTY', 'WINDOW', []),
+
     ('View3D Gesture Circle', 'EMPTY', 'WINDOW', []),
     ('Gesture Straight Line', 'EMPTY', 'WINDOW', []),
     ('Gesture Zoom Border', 'EMPTY', 'WINDOW', []),