Remove "/a" from GET_CHECKERS_URL

* Server was returning 400 response for the url with /a

Change-Id: Id00b8f8d8f719e089c60372914a8acfdf533a79b
diff --git a/gr-checks/gr-checkers-list.js b/gr-checks/gr-checkers-list.js
index 0967c03..2542832 100644
--- a/gr-checks/gr-checkers-list.js
+++ b/gr-checks/gr-checkers-list.js
@@ -1,7 +1,7 @@
 (function() {
   'use strict';
   const CHECKERS_PER_PAGE = 15;
-  const GET_CHECKERS_URL = "/a/plugins/checks/checkers/";
+  const GET_CHECKERS_URL = "/plugins/checks/checkers/";
 
   /**
    * Show a list of all checkers along with creating/editing them