Maniphest - fix corner case where no-op subscriber change had wrong error

Summary: Fixes T6732. Fix is to stop trying to catch the error in the controller and let the editor do its job.

Test Plan: tried to add an existing subscriber and got an error message about how that wouldn't do anything

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T6732

Differential Revision: https://secure.phabricator.com/D11303

src/applications/maniphest/controller/ManiphestTransactionSaveController.php

@@ -131,12 +131,6 @@ final class ManiphestTransactionSaveController extends ManiphestController {
       }
     }
 
-    // Evade no-effect detection in the new editor stuff until we can switch
-    // to subscriptions.
-    $added_ccs = array_filter(array_diff(
-      $added_ccs,
-      $task->getSubscriberPHIDs()));
-
     if ($added_ccs) {
       // We've added CCs, so include a CC transaction.
       $all_ccs = array_merge($task->getSubscriberPHIDs(), $added_ccs);