APCu is now provided by base image
Summary: We moved the APCu extension to the nasqueron/php-fpm base image.
Test Plan: php -l to ensure APCu is loaded
Reviewers: Kaliiixx
Subscribers: Nasqueron Docker deployment squad
Projects: Docker images
Maniphest Tasks: T604
Differential Revision: http://devcentral.nasqueron.org/D98