Updated `.arcconfig` to match newer style configuration.

Summary: If I'm not mistaken, `project_id` was recently replaced by `project.name` and `conduit_uri` replaced by `phabricator.uri`.

Test Plan: I guess if this differential works, then everything is okay.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D8334