Prune shellserver/PHP7 unit

Summary:
Contains only a cgi.force_redirect = 0 for SuEXEC, unused.

Plan is to use nginx + php-fpm ondemand if PHP hosting is asked on Eglide.

Ref T1325.

Test Plan: no op

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1325

Differential Revision: https://devcentral.nasqueron.org/D1476