Use the dedicated function `rb_io_check_io`

process.c

@@ -1840,7 +1840,7 @@ check_exec_redirect_fd(VALUE v, int iskey)
         else
             goto wrong;
     }
-    else if (!NIL_P(tmp = rb_check_convert_type_with_id(v, T_FILE, "IO", idTo_io))) {
+    else if (!NIL_P(tmp = rb_io_check_io(v))) {
         rb_io_t *fptr;
         GetOpenFile(tmp, fptr);
         if (fptr->tied_io_for_writing)