patch 8.1.0726: redrawing specifically for conceal feature

Problem:    Redrawing specifically for conceal feature.
Solution:   Use generic redrawing methods.
diff --git a/src/window.c b/src/window.c
index e67aeea..5989aed 100644
--- a/src/window.c
+++ b/src/window.c
@@ -4177,9 +4177,9 @@
     win_enter(wp, TRUE);
 
 #ifdef FEAT_CONCEAL
-    /* Conceal cursor line in previous window, unconceal in current window. */
+    // Conceal cursor line in previous window, unconceal in current window.
     if (win_valid(owp) && owp->w_p_cole > 0 && !msg_scrolled)
-	update_single_line(owp, owp->w_cursor.lnum);
+	redrawWinline(owp, owp->w_cursor.lnum);
     if (curwin->w_p_cole > 0 && !msg_scrolled)
 	need_cursor_line_redraw = TRUE;
 #endif