Hi,
If you edit the file product / cart via the menu Display>Views, you have this line:
<th></th>
This empty header is there for the delete icon column, so we decided not to put a title there. The delete button on each row is self explanatory.
Note that I checked your URL and I see that you have a class on that "th" tag while we don't in the default view. So you might have some kind of override there already with some different code... Just look for the </th> tag in the code and you should find it.