patch 8.2.4698: Vim9: script variable has no flag that it was set

Problem:    Vim9: script variable has no flag that it was set.
Solution:   Add a flag that it was set, to avoid giving it a value when used.
            (closes #10088)

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4698,
 /**/
     4697,
 /**/