patch 8.2.4509: Vim9: can declare a variable with ":va"

Problem:    Vim9: can declare a variable with ":va".
Solution:   Disallow using ":va", require using ":var".
diff --git a/src/version.c b/src/version.c
index 5bbd307..999f8ac 100644
--- a/src/version.c
+++ b/src/version.c
@@ -755,6 +755,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4509,
+/**/
     4508,
 /**/
     4507,