R1:b445e1d80df9

Fix config transaction rendering error on auth page by allowing PhutilSafeHTML

Summary: Closes T15706

Test Plan: Checked that the page worked as expected with changes implemented

Reviewers: O1 Blessed Committers, speck, valerio.bozzolan

Reviewed By: O1 Blessed Committers, speck, valerio.bozzolan

Subscribers: sirocyl, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Maniphest Tasks: T15706

Differential Revision: https://we.phorge.it/D25512