This should work, but it looks like there is a typo.
$("[title|='Remove']").hide();
This will work
$("[title ='Remove']").hide();
It likely doesn't matter as the human eye can't tell the difference, but the options below use a jQuery selector that is a little more specific which in theory will perform better. ...
Hide the button with the X
$("button.k-upload-action[aria-label='Remove']").hide()
Remove the button with the X from the DOM altogether.
$("button.k-upload-action[aria-label='Remove']").remove()