title: DRF - `write_only=True` displays in response schema
body: <p>I'm using <a href="https://github.com/axnsan12/drf-yasg" rel="noreferrer">drf-yasg</a> to document my APIs. However, I'm running into a problem</p>
  
  <p>I've a serializer in which one of the fields is set to <code>write_only=True</code>. </p>
  
  <pre><code>class XYZSerializer(serializers.ModelSerializer):
      status = serializers.BooleanField(default=True, write_only=True)
  
      class Meta:
  
          model = XYZ
          fields = ('id', 'status')
  </code></pre>
  
  <p>When generating the swagger docs, field <code>status</code> still shows in the Response fields. Technically, it should not.</p>
  
  <p>How to correct this?</p>