CODE_OF_CONDUCT.md: update PLC members list

As part of our code of conduct, we maintain a list of active members on the Project Leadership Committee, which serves a couple of purposes. The details are in 3f9ef874a7 (CODE_OF_CONDUCT: mention individual project-leader emails, 2019-09-26), but the gist is as follows: - It makes it clear that people with a CoC complaint may contact members individually as opposed to the general PLC list (in case the subject of their complaint has to do with one of the committee members). - It also serves as the de-facto list of people on the PLC, which isn't committed anywhere else in the tree. As of [1], Peff is no longer a member of Git's Project Leadership Committee. Let's update the list of active members accordingly [2]. This also gives us a convenient opportunity to thank Peff for his many years of service on the PLC, during which he helped the Git community in more ways than we can easily list here. [1]: https://lore.kernel.org/git/YboaAe4LWySOoAe7@coredump.intra.peff.net/ [2]: https://lore.kernel.org/git/CAP8UFD2XxP9r3PJ4GQjxUbV=E1ASDq1NDgB-h+S=v-bZQ7DYwQ@mail.gmail.com/ Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>