patch 8.2.3569: error for :let when vimrc is Vim 9 script

Problem:    Error for :let when vimrc is Vim 9 script.
Solution:   Prepend :legacy in the code for converting arguments. (Christian
            Brabandt, closes #9068, closes #9077)
diff --git a/src/version.c b/src/version.c
index c42cd2a..ea1a790 100644
--- a/src/version.c
+++ b/src/version.c
@@ -758,6 +758,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3569,
+/**/
     3568,
 /**/
     3567,