patch 8.0.0286: not always redrawing after screen resize

Problem:    When concealing is active and the screen is resized in the GUI it
            is not immediately redrawn.
Solution:   Use update_prepare() and update_finish() from
            update_single_line().

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    286,
 /**/
     285,
 /**/