[FIX] web : attachment controller got unexpected args

On webclient, on 'Attachment(s)' dropdown (form view) when clicking on an attachment to download it, a request is sent to /web/content/ with a param 't' containing the current date. This param wasn't used neither before the new controller, but the old one accept additional kwargs. The new controller crashes, and since the t parameter is not used, removing it seems better.

addons/web/static/src/js/widgets/sidebar.js

@@ -179,7 +179,7 @@ var Sidebar = Widget.extend({
         _.each(attachments,function(a) {
             a.label = a.name;
             if(a.type === "binary") {
-                a.url = '/web/content/'  + a.id + '?download=true&t=' + (new Date().getTime());
+                a.url = '/web/content/'  + a.id + '?download=true';
             }
         });
         this.items.files = attachments;