title: layout UILabel after assigning a value for attributedString property
body: <p>I have a function that returns <code>NSMutableAttributedString</code> to style a <code>UILabel</code> in <code>UITableViewCell</code>.</p>
  
  <p>To solve this issue, I run that code in main thread as following</p>
  
  <pre><code>DispatchQueue.main.async {
       self.titleLabel.attributedText = UITableViewCell.timelineTitle(prefix: "#Meeting: ", title: title, prefixColor: UIColor(hex: "#FF3B71"))
  }
  </code></pre>
  
  <p>but now, the titleLabel start acquiring bigger space. It looks like cells are not re-calculate cell layout. <code>label.sizeToFit()</code> doesn't fix the issue!</p>