Revert partial/nonfunctional OpenGraph support
Ref T13018. See that task and the Discourse thread for discussion.
This doesn't work as-is and we need to og:description everything to make it work. I don't want to sink any more time into this so just back all the changes out for now.
(The <html> change is unnecessary anyway.)
Test Plan: Strict revert.
Reviewed By: amckinley
Maniphest Tasks: T13018
Differential Revision: https://secure.phabricator.com/D18782