title: Removing the title from a QGroupBox
body: <p>Is it possible to completely remove the title from a <code>QGroupBox</code>? If you just give it an empty title, the label where the title would be still takes up space. It looks like this:</p>
  
  <p><a href="https://i.stack.imgur.com/N27MT.png" rel="noreferrer"><img src="https://i.stack.imgur.com/N27MT.png" alt="enter image description here"></a></p>
  
  <p>But I want it to look like this instead:</p>
  
  <p><a href="https://i.stack.imgur.com/0QKl4.png" rel="noreferrer"><img src="https://i.stack.imgur.com/0QKl4.png" alt="enter image description here"></a></p>
  
  <p>I tried the following things without success:</p>
  
  <ul>
  <li>Setting the title font size to zero</li>
  <li>Giving the title a size of zero in the stylesheet via <code>setStyleSheet("QGroupBox:title{ max-width: 0; max-height: 0; }");</code></li>
  <li>Moving the title inside the box via <code>setStyleSheet("QGroupBox:title{ subcontrol-position: center center;}")</code></li>
  </ul>
  
  <p>Note: You might say that a group box without title is a use case for <code>QFrame</code>. The problem with this is that I want to mix groups/frames with and without title, but the frame has a different visual style than the group box. So if you could tell me how to make <code>QFrame</code> look like <code>QGroupBox</code> that would solve my problems too.</p>