patch 8.2.1391: Vim9: no error for shadowing a script function

Problem:    Vim9: no error for shadowing a script function.
Solution:   Check for already defined items. (closes #6652)
diff --git a/src/version.c b/src/version.c
index 8b68bc1..978920e 100644
--- a/src/version.c
+++ b/src/version.c
@@ -755,6 +755,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1391,
+/**/
     1390,
 /**/
     1389,