patch 8.2.3753: Vim9: function unreferenced while called is never deleted

Problem:    Vim9: function unreferenced while called is never deleted.
Solution:   Delete a function when no longer referenced.
diff --git a/src/userfunc.c b/src/userfunc.c
index 7fc764e..4f86c07 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -2281,7 +2281,7 @@
  * Free all things that a function contains and free the function itself.
  * When "force" is TRUE we are exiting.
  */
-    static void
+    void
 func_clear_free(ufunc_T *fp, int force)
 {
     func_clear(fp, force);