Retiring as maintainer

[arjun024]

Hi @paketo-buildpacks/php-maintainers
I'd like to announce I will be retiring from my role as maintainer of the PHP subteam effective 2021/Dec/10 (a week from today). I'd like to continue in the subteam as a contributor.

[arjun024]

Effective now. cc @paketo-buildpacks/steering-committee

[dmikusa]

Thanks for your time on the team. I've moved you from the maintainer team to the contributor team.