Remove orphan CSS selectors in slowvote/slowvote.css
Summary:
* slowvote-header-content
** Added in https://we.phorge.it/rP89ee928a51c72d9fda17a59f73b060a92cc0c665, usage removed in https://we.phorge.it/rPaa22a578d01b8b5c69c89b9dc4a370552534f6dd from `src/applications/slowvote/view/SlowvoteEmbedView.php`
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/D26003