CSS: Fix typo in property name in phui-action-panel.css
Summary: `.phui-action-panel-subheader a` has `text-decoraction: none`. The author very likely had a `text-decoration` in mind instead.
Test Plan: Probably go to http://phorge.localhost/uiexample/view/PHUIActionPanelExample/ and edit one of those boxes to include a `<a>` instead of a `<span>`. I did not.
Reviewers: O1 Blessed Committers, mainframe98
Reviewed By: O1 Blessed Committers, mainframe98
Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Differential Revision: https://we.phorge.it/D26468