Use standard subscribers effects in Herald Adapter for Phriction

Summary: Ref T8455. Instead of using an ad-hoc subscribers effect in Phriction, use the new standard one (introduced previously; this depends on D13178).

Test Plan:

• Wrote an "add subscribers" Herald rule, updated a Phriction document, saw it apply its effect.
• Observed availability of "remove" subscribers actions.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T8455

Differential Revision: https://secure.phabricator.com/D13180