patch 8.2.0650: Vim9: script function can be deleted

Problem:    Vim9: script function can be deleted.
Solution:   Disallow deleting script function.  Delete functions when sourcing
            a script again.
diff --git a/src/version.c b/src/version.c
index fa91a2b..d58ef8a 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    650,
+/**/
     649,
 /**/
     648,