In Differential, filter repository operations to just "Land" operations again

Summary:
Reverts D18276. See PHI18 for discussion. The additional rules here (roughly, "only show the first successful operation") didn't actually work out for the other types of operations.

This is all just figuring out a stopgap, T12935 and other changes should eventually provide real pathways here.

Test Plan: Straight revert.

Reviewers: chad

Reviewed By: chad

Differential Revision: https://secure.phabricator.com/D18281