Clean up Multirow Manager UI

Summary: Fixes T4234 (Policy and Herald). I will have an additional diff for Maniphest Batch Editor, which looks jank in many other ways.

Test Plan:
Test editing a policy and some herald rules. Stuff lines up better.

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{F235087}

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T4234

Differential Revision: https://secure.phabricator.com/D10864