Use non-proxied links

appengine/swarming/elements/res/imp/tasklist/task-list.html

 <!--
   Copyright 2016 The LUCI Authors. All rights reserved.
   Use of this source code is governed under the Apache License, Version 2.0
   that can be found in the LICENSE file.
 
   This in an HTML Import-able file that contains the definition
   of the following elements:
 
     <task-list>
 
@@ skipping 311 matching lines @@
         }
         return retVal;
       },
 
       _cannotCancel: function(task, permissions) {
         return !(permissions && permissions.cancel_task &&
               this._column("state", task) === "PENDING");
       },
 
       _cancelTask: function() {
-        var url = "/_ah/api/swarming/v1/task/" + this._toCancel +"/cancel";
+        var url = "/api/swarming/v1/task/" + this._toCancel +"/cancel";
         swarming.postWithToast(url, "Canceling task " + this._toCancel, this._auth_headers);
         this.set("_toCancel", "");
       },
 
       _promptClosed: function(e) {
         if (e.detail.confirmed) {
           this._cancelTask();
         }
       },
 
@@ skipping 15 matching lines @@
         return task.tagMap[col];
       },
 
       _taskClass: function(task) {
         return this.stateClass(this._column("state", task));
       }
     });
   })();
   </script>
 </dom-module>