R1:d12be0fc2190

Change Pholio editor access modifier

Summary: Used by `PholioImageFileTransaction::mergeTransactions()`. I forgot to test adding multiple images to a Mock at the same time after migrating `mergeTransactions` over to the modular framework.

Test Plan: Added multiple images in a single transaction and didn't get an exception about accessing a protected function.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley

Differential Revision: https…