Fix the border of font selectors

The top border was shorter than the others, fixed by using CSS
applied to the first element instead of the parent.

Bug: T136273
Change-Id: Ic894ef99ef2c88a23d6db65b68327fd903473038

resources/css/ext.uls.displaysettings.less

@@ -31,14 +31,16 @@ div.display-settings-block {
 
 .uls-display-settings-font-selectors {
 	margin: 5px 0 15px 0;
-	border-top: 1px solid #eee;
 }
 
 .uls-font-item {
 	border-bottom: 1px solid #eee;
 	background: #fbfbfb;
-	margin: 0;
 	padding: 10px 0;
+
+	&:first-child {
+		border-top: 1px solid #eee;
+	}
 }
 
 .uls-font-label,