title: Pyside2 QTextBrowser overwriteMode does not replace old text
body: <p>I'm using the PySide2 package and found that the <code>overwriteMode</code> won't work in my code. Here is what I wrote:</p>
  
  <pre><code>self.ui.textBrowser.setOverwriteMode(True)
  self.ui.textBrowser.insertPlainText('test1\ntest2\ntest3')
  self.ui.textBrowser.moveCursor(QTextCursor.Start)
  self.ui.textBrowser.insertPlainText('hhh')
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/yDJrJ.png" rel="nofollow noreferrer">Complete source code</a></p>
  
  <p>I used Qt-Creator to design my GUI and my settings for the QTextBrowser looks like that:</p>
  
  <p><a href="https://i.stack.imgur.com/RwWeu.png" rel="nofollow noreferrer">QTextBrowser settings</a></p>
  
  <p>I got the following output:</p>
  
  <p><a href="https://i.stack.imgur.com/Y84F4.png" rel="nofollow noreferrer">Output</a></p>
  
  <p>As you can see, the first line should be 'hhht1' but it gives 'hhhtest1'. </p>
  
  <p>I'm testing this with PySide2 version 5.11.2 on a Windows 10.</p>
  
  <p>I am new to Qt and can anyone please help me out? What am I missing? Thank you!</p>