meta: move jbergstroem to emeritus

jbergstroem confirmed in email that they should go to collaborator
emeritus. They still have their toe in the Build WG and will stay on
there. Who knows, maybe they'll be back as a Collaborator before we know
it.

PR-URL: https://github.com/nodejs/node/pull/31996


Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>