Fix typo in Phabricator containers configuration

Summary:
ports_bindings → port_bindings

Currently, ports aren't exposed per this typo.

This is a follow-up for change 6ff8c89d50db.

Test Plan: nginx can now proxies the applications

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D1928