Hygiene: Some CSS clean-up. Removing old cruft and consolidating.

Removing some old CSS for cached pages that is no longer needed.

Consolidating duplicate .content-header selectors in specials/
common.less.

Change-Id: I52116665f3d9bf72ac099fc49967979744e894ea
Merge "Hygiene: Some CSS clean-up. Removing old cruft and consolidating."