Remove shadow from slave cards

Were leftover from the older, more round style and don't fit to the new, straight look

css/gui/slaveList/cardStyle.css

 .card {
 	border: 2px solid #333333;
 	background-color: #1a1a1a;
-	box-shadow: 10px 10px 10px black,
-		-10px 10px 10px black;
 	padding: 1em;
 	margin-bottom: 1em;
 }