Remove about page from defaults and add XXX for future pages

lib/defaults.js

@@ -50,13 +50,12 @@ Default.httpHeaders = function () {
         "Access-Control-Allow-Origin": "*",
     };
 };
-
+// XXX check here for any deleted pages
 Default.mainPages = function () {
     return [
         'index',
         'privacy',
         'terms',
-        'about',
         'contact',
         'what-is-cryptpad',
         'features',