Removed extra space from Maniphest email subject line.

Summary:
Like the title says.

Test Plan:
grep for ':  ' didn't reveal any other similar problems.

Reviewed By: jungejason
Reviewers: epriestley, jungejason
CC: jungejason
Differential Revision: 121

src/applications/maniphest/editor/transaction/ManiphestTransactionEditor.php

@@ -180,7 +180,7 @@ class ManiphestTransactionEditor {
 
     id(new PhabricatorMetaMTAMail())
       ->setSubject(
-        '[Maniphest] T'.$task->getID().' '.$action.':  '.$task->getTitle())
+        '[Maniphest] T'.$task->getID().' '.$action.': '.$task->getTitle())
       ->setFrom($transaction->getAuthorPHID())
       ->addTos($email_to)
       ->addCCs($email_cc)