craft-cp-css.css

#fields .field:not(:last-child):after {
	background-color: #e3e5e8;
    content: '';
	display: block;
	height: 1px;
	margin-top: 32px;
	position: relative;
	left: -24px;
	width: calc(100% + 48px);
}

#fields .matrix .field:after,
#fields .input .field:after
{
	display: none;
	height: 0;
	margin: 0;
}