php-fpm: remove user/group defs

we're not running as root after all

images/php-fpm/www.conf

@@ -6,11 +6,7 @@ pid = /run_local/php-fpm.pid
 error_log = /proc/self/fd/2
 
 [www]
-user = www-data
-group = www-data
 listen = /run_local/php-fpm.sock
-listen.owner = www-data
-listen.group = www-data
 pm = dynamic
 pm.max_children = 8
 pm.start_servers = 2