Deemphasise line numbers in rich text

services/web/public/stylesheets/app/editor/rich-text.less

@@ -13,6 +13,10 @@
     padding: 0 8%;
   }
 
+  .CodeMirror-linenumber {
+    font-size: 0.8em;
+  }
+
   // TODO: Change prefix away from wl- ?
 
   /****************************************************************************/