A temporary css cleanup to hold us over till a proper css overhaul.

Summary: Ref T8187, A temporary css cleanup to hold us over till a proper css overhaul.

Test Plan: Mostly, confirm that long event names don't break the calendar month view.

Reviewers: chad, #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T8187

Differential Revision: https://secure.phabricator.com/D12908