Fix typo in "button"

Test Plan: Observation.

Reviewers: #blessed_reviewers, amckinley, epriestley

Reviewed By: #blessed_reviewers, amckinley, epriestley

Subscribers: Korvin, amckinley, epriestley

Differential Revision: https://secure.phabricator.com/D19483

src/applications/daemon/controller/PhabricatorDaemonBulkJobMonitorController.php

···
           ->appendParagraph(
             pht(
               'This job is waiting for confirmation before work begins.'))
-          ->addCancelButotn($job->getManageURI(), pht('Details'));
+          ->addCancelButton($job->getManageURI(), pht('Details'));
       }
     }