Change owner of .env to php-fpm user

Summary:
As a chmod 400 file, .env isn't really useful if it belongs to root.

This is a follow-up for 8e263846862b.

Ref T1828.

Test Plan: Deploy on web-001, ensure files belong to relevant app user

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1828

Differential Revision: https://devcentral.nasqueron.org/D3072