removed box shadow on embed xmls

cms/static/sass/_assets.scss

@@ -69,6 +69,7 @@
       }
 
       .embeddable-xml-input {
+        @include box-shadow(none);
         width: 100%;
       }
 
@@ -181,6 +182,7 @@
   }
 
   .embeddable-xml-input {
+    @include box-shadow(none);
     width: 400px;
   }