doc: move shigeki to emeritus

In email, Shigeki Ohtsu indicated that a move to emeritus would be
appropriate at this time. I'm especially grateful for the crypto and
security work over the years, and I'm sure I'm not the only one.

PR-URL: https://github.com/nodejs/node/pull/36093


Reviewed-By: Shigeki Ohtsu <ohtsu@ohtsu.org>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>