Minor fix for `CelerityManagementMapWorkflow`

Summary: `phutil_var_export` only accepts a single parameter. This bug was introduced in D9926.

Test Plan: Eye-ball it.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9930