retire chi-node-05

in #40377 (closed), we found significant hardware issues with chi-node-05. it was marked as offline in ganeti, and it's agreed we keep it for parts, but we should just completely retire the host per our normal procedure.

checklist:

1. announcement (N/A)
2. nagios
3. retire the host in fabric
4. remove from LDAP with ldapvi
5. power-grep
6. remove from tor-passwords
7. remove from DNSwl (N/A)
8. remove from docs (modify https://gitlab.torproject.org/tpo/tpa/team/-/wikis/howto/new-machine-cymru#servers particularly, but also spreadsheet)
9. remove from racks (N/A, keep for spares)
10. remove from reverse DNS