Make new JIRA Issues field editable

Summary: Ref T2222. This updates the new JIRA field to be editable.

Test Plan: Used `/editpro/` to edit associated JIRA issues.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2222

Differential Revision: https://secure.phabricator.com/D8364