Convert AphrontErrorView to safe HTML

Summary: Done by searching for `AphrontErrorView` and then `appendChild()`.

Test Plan:
Looked at Commit Detail.
Looked at Revision Detail.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2432

Differential Revision: https://secure.phabricator.com/D4843

src/applications/herald/controller/HeraldTranscriptController.php

@@ -35,8 +35,10 @@ final class HeraldTranscriptController extends HeraldController {
       $notice = id(new AphrontErrorView())
         ->setSeverity(AphrontErrorView::SEVERITY_NOTICE)
         ->setTitle('Old Transcript')
-        ->appendChild(
-          '<p>Details of this transcript have been garbage collected.</p>');
+        ->appendChild(phutil_tag(
+          'p',
+          array(),
+          'Details of this transcript have been garbage collected.'));
       $nav->appendChild($notice);
     } else {
       $filter = $this->getFilterPHIDs();