Tidy paths for `require_once`

Summary: Use `..` instead of `dirname()`. I think that this is much neater.

Test Plan: Ran all of the affected scripts.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9969