Make columns in flag view not squish each other

Summary:
Unlike (all? most?) other tables, the flag table has two wide
columns: the object name and the flag note. This fiddles with the
classes so neither gets squished too much by the other.

This is kind of a hack and I don't even know if it's cross-browser
compatible because I only have WebKit here. But maybe it's fine.

Test Plan:
View Differential home page while changing revision names and
flag notes to weird things.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T1586

Differential Revision: https://secure.phabricator.com/D3128