resolve shutdown_workers to workers_shutdown (#4064)

Author: EamonTracey

taskvine/src/bindings/python3/ndcctools/taskvine/manager.py

@@ -156,7 +156,7 @@ def _free(self):
         try:
             if self._taskvine:
                 if self._shutdown:
-                    self.shutdown_workers(0)
+                    self.workers_shutdown(0)
                 self._update_status_display(force=True)
                 cvine.vine_delete(self._taskvine)
                 self._taskvine = None