Replace HeraldActionConfig::getActionMap() in HeraldTranscriptController

Summary:
D1449 removed HeraldActionConfig::getActionMap(), but it was still used in
HeraldTranscriptController. This fixes the controller to use the method that
replaced getActionMap.

Test Plan: loaded a herald transcript

Reviewers: epriestley, xela

Reviewed By: epriestley

CC: aran

Differential Revision: https://secure.phabricator.com/D1466