PB-500 static test fixes

Author: paras89

app/code/Magento/PageBuilder/view/adminhtml/web/css/source/content-type/_preview.less

@@ -195,17 +195,13 @@
     border: 15px solid @color-gray98;
     box-shadow: @pagebuilder-affordance-box-shadow; // #ebebeb
     padding: 0;
-
-    &:not(.pagebuilder-column):not(.pagebuilder-column-group):before {
-        display: none;
-    }
-
+    
     &:not(
     .pagebuilder-column,
     ) {
         &:not(
         .pagebuilder-column-group
-        ){
+        ) {
             &:before {
                 display: none;
             }