I don't quite sure what you are expecting. If you want two lines max, there should be no 3rd line.
Use this:
self.text_description.textContainer.maximumNumberOfLines = 2
self.text_description.textContainer.lineBreakMode = .byTruncatingTail
Limit the number of lines for UITextview
It seems what you actually want is a textview with two lines height? If that is true, try this in you view controller.
self.text_description = UITextView(frame: CGRect(x: 100.0, y: 100.0, width: 200.0, height: 28.0))
self.text_description.backgroundColor = #colorLiteral(red: 0.8039215803, green: 0.8039215803, blue: 0.8039215803, alpha: 1)
self.view.addSubview(self.text_description)