input: Write a function to create a REST API in Python that allows deletion of an item from a list. Use Flask to define routes and handle HTTP methods.
  assert app.test_client().delete('/items/Banana').get_json()=={"message":"Item successfully deleted."}
  assert app.test_client().delete('/items/Grapes').get_json()=={"message":"Item not found."}
output: 
  items = ["Apple", "Banana", "Cherry"]
  
  @app.route('/items/<string:item>', methods=['DELETE'])
  def delete_item(item):
      if item in items:
          items.remove(item)
          return jsonify({"message": "Item successfully deleted."})
      else:
          return jsonify({"message": "Item not found."})
  