R1:4ae28837fde1

Update Conpherence CSS to handle multiple edits better

Summary: Fixes T7655. We'll set tighter spacing around edit clusters. Also darkened up the date marker and remove unused `phabricator-transaction-view` CSS that was still scattered around the site.

Test Plan: Test a full and column multi-edit spam. Visited Ponder and Diffusion, noticed no issues using those apps. Grepped for other users of `phabricator-transaction-view`

Reviewers: epriestley, btrahan

Reviewed By: btrahan

Subscribers: Korvin…