patch 8.2.1126: Vim9: using :copen causes an error

Problem:    Vim9: using :copen causes an error.
Solution:   Add flag LET_NO_COMMAND in set_var().
diff --git a/src/version.c b/src/version.c
index b36f248..d1607ae 100644
--- a/src/version.c
+++ b/src/version.c
@@ -755,6 +755,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1126,
+/**/
     1125,
 /**/
     1124,