MINOR Don't invoke layout() in onmatch() for cms-preview, as it cause…

…s a gap above the menu/logo div for some reason. It's also unnecessary processing, since the preview is always hidden by default, and layout() will be triggered through redraw() when required (e.g. preview panel expansion)

admin/javascript/LeftAndMain.Preview.js

@@ -76,8 +76,6 @@
 					if(!self.hasClass('is-collapsed')) self.collapse();
 				});
 
-				this.layout({type: 'border'});
-
 				if(this.hasClass('is-expanded')) this.expand();
 				else this.collapse();
 				this.data('cms-preview-initialized', true);