You should use
overflow-y: hidden
as folows
$('textarea').css("height", $("textarea").prop("scrollHeight"))textarea {
  width: 300px;
  resize: none;
  margin: 0;
  padding: 0;
  overflow-y: hidden;
}<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<textarea>
Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a </textarea>
solved How to remove bottom padding in textarea? [closed]