patch 8.0.1618: color Grey50 is missing in the compiled-in table

Problem:    Color Grey50, used for ToolbarLine, is missing in the compiled-in
            table.
Solution:   Add the color to the list. (Kazunobu Kuriyama)

src/version.c

@@ -766,6 +766,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1618,
 /**/
     1617,
 /**/