patch 8.2.2033: Vim9: :def without argument gives compilation error

Problem:    Vim9: :def without argument gives compilation error.
Solution:   Add the DEF instruction. (closes #7344)
diff --git a/src/userfunc.c b/src/userfunc.c
index 7a306b1..70bbf33 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -2748,7 +2748,7 @@
  * List functions.  When "regmatch" is NULL all of then.
  * Otherwise functions matching "regmatch".
  */
-    static void
+    void
 list_functions(regmatch_T *regmatch)
 {
     int		changed = func_hashtab.ht_changed;