Stepping down from seccomp mintainership

[Eduardo Otubo]

Hello all,

It's been a while since my last commit or pull request, and given the
current state of things I don't think I'll be coming back to actual
QEMU development. At least not as frequently as I wanted to have
seccomp under my eyes at all times.

This being said, I'd like to retire as the seccomp maintainer. Anyone
who wishes to take over from here is welcome to do so.

Thank you all,

--
Eduardo