Restore original more menu padding in legacy Vector

One of the goals with desktop improvements is to not make any
visible changes to the original Vector skin.

In T289163 we wrapped links in a span, and moved the font-size
declaration to the span. The padding of the link is now applying
with font-size 16px.

Bug: T289163
Change-Id: Ifbf6f7a4c5cb6fda6389b33fc9962bdb03dd1f43

resources/skins.vector.styles.legacy/components/MenuDropdown.less

@@ -1,3 +1,6 @@
+@import '../../common/variables.less';
+@import 'mediawiki.mixins.less';
+
 // Extends the common MenuDropdown, but allows it to be opened via hover.
 
 .vector-menu-dropdown:not( .vector-user-menu ) {
@@ -12,3 +15,12 @@
 		transform: scaleY( -1 );
 	}
 }
+
+.vector-menu-dropdown {
+	li {
+		a {
+			// Historic value.
+			padding: unit( ( 8.125px / @font-size-browser ), em );
+		}
+	}
+}