patch 8.2.3177: Vim9: can not use "for _ in expr" at script level

Problem:    Vim9: can not use "for _ in expr" at script level.
Solution:   Skip assignment if the loop variable is "_".
diff --git a/src/version.c b/src/version.c
index c1a4f3f..0eb4b44 100644
--- a/src/version.c
+++ b/src/version.c
@@ -756,6 +756,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3177,
+/**/
     3176,
 /**/
     3175,