[simple theme] add .rounded-corners to selectable_url

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

searx/static/themes/simple/src/less/toolkit.less

@@ -111,6 +111,7 @@ div.selectable_url {
   overflow: hidden;
   height: 1.2em;
   line-height: 1.2em;
+  .rounded-corners-tiny;
 
   pre {
     .pre();