patch 8.2.4371: Vim9: can create a script variable from a legacy function

Problem:    Vim9: can create a script variable from a legacy function.
Solution:   Disallow creating a script variable from a function.
diff --git a/src/version.c b/src/version.c
index b7fbbbd..3edb62d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4371,
+/**/
     4370,
 /**/
     4369,