Ignore SC2038 EUID shellcheck issue

Summary:
$EUID is used to determine if a command is run as root. ShellCheck
reports every POSIX shell should have it, but that's not the case
of all dash versions.

Test Plan: arc lint roles/webserver-alkane/php/files/restart-php-fpm.sh

Reviewers: DorianWinty

Reviewed By: DorianWinty

Differential Revision: https://devcentral.nasqueron.org/D3350