Fix visibility of the LiskDAO::willWriteData method

Summary: Ref T6822.

Test Plan: `grep`. This method is only called from `LiskDAO::update()`.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Maniphest Tasks: T6822

Differential Revision: https://secure.phabricator.com/D11409

src/applications/releeph/storage/ReleephBranch.php

@@ -67,7 +67,7 @@ final class ReleephBranch extends ReleephDAO
     return $this;
   }
 
-  public function willWriteData(array &$data) {
+  protected function willWriteData(array &$data) {
     // If symbolicName is omitted, set it to the basename.
     //
     // This means that we can enforce symbolicName as a UNIQUE column in the