Remove orphan CSS selectors in phui/phui-document*.css
Summary:
* `phui-document-box`
** Added in https://we.phorge.it/rPf5a7e8bdbd9a6d68514bb0b08a4a7d626ca7044b, usage removed in https://we.phorge.it/rPbf227f77a5dc928f1380e4bc81059f83cfb96548
* `phui-document-properties`
** Added in https://we.phorge.it/rPc45ba304168239f0600d780476dc705b54b6f492, usage removed in https://we.phorge.it/rPa6e24cb2be9cc15a0eeacd6b90811c4b148c76ab
Test Plan: Grep the code for each CSS selector (`grep --exclude="*.css" -R 'some-search-string' .`), also do partial searches, get no results.
Reviewers: O1 Blessed Committers, valerio.bozzolan
Reviewed By: O1 Blessed Committers, valerio.bozzolan
Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Differential Revision: https://we.phorge.it/D26014