remove unused code related to removed deprecated RPC fields

Summary:
We left some unused code when removing deprecated fields from getpeerinfo

This is a partial backport of core#20755
This is a backport of core#20791

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D13267