[Redesign] Use normal sized buttons for Changesets

Summary: Ref T8099, No specific reason for these to be small buttons.

Test Plan: Test desktop and mobile layouts.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T8099

Differential Revision: https://secure.phabricator.com/D13081