Add concealed text limitation to documentation

Author: dstein64

doc/scrollview.txt

@@ -268,10 +268,12 @@ scrollview_hide_on_text_intersect          *scrollview_hide_on_text_intersect*
                        intersect with text. The functionality may not work for
                        lines where the last character spans multiple cells
                        (only the first cell of the character would be
-                       considered for intersection). The processing demands
-                       when enabling this option may result in noticeable lag
-                       under certain environments, especially on older
-                       hardware. Defaults to |v:false|.
+                       considered for intersection). For lines with concealed
+                       text, signs and the scrollbar can become hidden when
+                       they otherwise wouldn't intersect text. The processing
+                       demands when enabling this option may result in
+                       noticeable lag under certain environments, especially
+                       on older hardware. Defaults to |v:false|.
 
 scrollview_hover                           *scrollview_hover*
                        |Boolean| specifying whether the highlighting of