Remove celerity.resource-path config

Summary: Ref T4222. This was used by Facebook while developing Releeph, but should no longer be necessary since Releeph is in the upstream. I can't get an answer out of Facebook about whether they still use it or not (see T4227), so nuke it. We're going to replace it with a more general mechanism (see T4222).

Test Plan: Regenerated celerity map. Browsed some pages, still got resources.

Reviewers: btrahan, hach-que

Reviewed By: hach-que

CC: aran

Maniphest Tasks: T4222

Differential Revision: https://secure.phabricator.com/D7863