Add missing execution on archived task query

Summary: Fixes T8599. I'm not sure how to reproduce the original issue, but I'm fairly confident that the issue is that the issue is that `execute()` is not called on the query object.

Test Plan: Created a Harbormaster build plan with a single "Lease Host" step. Ran `./bin/harbormaster build --plan 1 D1` from the command line and hit the exception as described in T8599. Applied patch and hit a different exception (which I think is just because I don't know how to use #drydock and #harbormaster).

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: hach-que, epriestley, Korvin

Maniphest Tasks: T8599

Differential Revision: https://secure.phabricator.com/D13335

Author: joshuaspence

src/infrastructure/daemon/workers/PhabricatorWorker.php

@@ -199,7 +199,8 @@ final public static function waitForTasks(array $task_ids) {
     }
 
     $tasks = id(new PhabricatorWorkerArchiveTaskQuery())
-      ->withIDs($task_ids);
+      ->withIDs($task_ids)
+      ->execute();
 
     foreach ($tasks as $task) {
       if ($task->getResult() != PhabricatorWorkerArchiveTask::RESULT_SUCCESS) {