Logo shouldn't import layout

This explains a few issues that were occuring in the storybook
relating to modern/legacy.

Follow up to 5195f5fd6 which doesn't reference why.

Components should not import styles relating to one of the Vector
versions. They should all be self contained.

Change-Id: I6f9ef974be97f8be593cd2b79ce37c3e517d549f

resources/skins.vector.styles/Logo.less

@@ -1,6 +1,5 @@
 @import '../../variables.less';
 @import 'mediawiki.mixins.less';
-@import './layout.less';
 
 .mw-logo {
 	.flex-display();