U4-9055 remove background-color on preview that was interfering with the website

style

src/Umbraco.Web.UI.Client/src/less/canvas-designer.less

@@ -21,7 +21,6 @@ body {
     font-size: 14px;
     line-height: 20px;
     color: #343434;
-    background-color: #F5F5F5;
     -webkit-transition: all 0.2s ease-in-out;
     -moz-transition: all 0.2s ease-in-out;
     transition: all 0.2s ease-in-out;