patch 8.2.0085: dead code in builtin functions

Problem:    Dead code in builtin functions.
Solution:   Clean up the code.
diff --git a/src/textprop.c b/src/textprop.c
index fa3830c..dfd30dd 100644
--- a/src/textprop.c
+++ b/src/textprop.c
@@ -885,7 +885,7 @@
  * prop_type_get({name} [, {bufnr}])
  */
     void
-f_prop_type_get(typval_T *argvars, typval_T *rettv UNUSED)
+f_prop_type_get(typval_T *argvars, typval_T *rettv)
 {
     char_u *name = tv_get_string(&argvars[0]);