Summary:
Ref T5885. See D10276.
Currently, ActionHeaders can only have minicons, and we don't use them anywhere and they probably don't make much sense in the product anymore.
Instead, allow them to have font icons. Remove minicons, which have no callsites and probably won't in the future.
Test Plan:
{F190925}
- Grepped for `minicons`.
- Grepped for `setHeaderIcon()`.
Reviewers: btrahan, chad
Reviewed By: chad
Subscribers: epriestley
Maniphest Tasks: T5885
Differential Revision: https://secure.phabricator.com/D10277
eaacb4a511