Node editor: remove option to show overlapping Property region.

- The main window has sliders, which was drawn behind the region
- If property region had slider too, it got even worse.

Basically the node editor is UI view, so drawing another UI on top isn't
functioning well in general.

source/blender/editors/screen/area.c

@@ -917,7 +917,7 @@ static int region_is_overlap(wmWindow *win, ScrArea *sa, ARegion *ar)
 {
 	if (U.uiflag2 & USER_REGION_OVERLAP)
 		if (WM_is_draw_triple(win))
-			if (ELEM5(sa->spacetype, SPACE_VIEW3D, SPACE_IMAGE, SPACE_SEQ, SPACE_CLIP, SPACE_NODE))
+			if (ELEM4(sa->spacetype, SPACE_VIEW3D, SPACE_IMAGE, SPACE_SEQ, SPACE_CLIP))
 				if (ELEM3(ar->regiontype, RGN_TYPE_TOOLS, RGN_TYPE_UI, RGN_TYPE_TOOL_PROPS))
 					return 1;
 	return 0;