Fix a dashboard bucketing bug

Summary: Ref T10939. For various historical reasons, revision status is a numeric string. This comparison fails because it's (string) !== (int). Just use != so this will still work if we turn it into a real string in the future.

Test Plan: Tried a more specific test case locally, got better looking results in "Must Review" and "Should Review".

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10939

Differential Revision: https://secure.phabricator.com/D15928