patch 8.1.0768: updating completions may cause the popup menu to flicker

Problem:    Updating completions may cause the popup menu to flicker.
Solution:   Avoid updating the text below the popup menu before drawing the
            popup menu.
diff --git a/src/version.c b/src/version.c
index 719fd07..c6fe19d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -792,6 +792,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    768,
+/**/
     767,
 /**/
     766,