title: Remove panel border default css in ExtJS 5
body: <p>I want to remove panel border completely (border, background-image and all). I have a window which has 6 panel and every panel has title. I want only title name without any border.</p>
  
  <p>Question may be duplicate but i didn't get answer.</p>
  
  <p>I have tried border: false but doesn't work. </p>
  
  <p><a href="https://i.stack.imgur.com/RV6ap.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/RV6ap.png" alt="enter image description here"></a></p>