text: Title: On fields  if `pattern` parameter is added swagger execute request button when clicked has no effect
  Body: Here is the minimum code required to replay the error:
  
  ```python
  
  from flask import Flask, request
  from flask_restx import Resource, Api, fields
  
  app = Flask(__name__)
  api = Api(app)
  
  
  simple_email_model = api.model("email_model", dict(
      email=fields.String(required=True, pattern=".+@.+")
  ))
  
  
  @api.route('/email')
  class TestEmail(Resource):
  
      @api.expect(simple_email_model, validate=True)
      def post(self):
          return request.json
  
  
  
  if __name__ == '__main__':
      app.run(debug=True)
  
  ```
  
  I expect if pattern doesn't match the validation should fail.
  
  But, when I go to swagger-ui, complete the field and click on `Execute` button - nothing happens (the request is not made, button is freezed).
  
  
  ### **Environment**
  - Python version - 3.8
  - Flask version - 2.0.3 
  - Flask-RESTX version - 0.5.1
  
  