add border-radius to overbox on submit modal

services/web/public/stylesheets/app/editor/publish-modal.less

@@ -54,6 +54,7 @@
 	      background-color: white;
 	      margin-top: @line-height-computed / 2;
         border: 1px solid @gray-lighter;
+        border-radius: 9px;
     }
     .content-as-table {
 	      .table-content,