Remove the deprecated banscore field from the getpeerinfo RPC

Summary:
This is a follow up to D10802. This has been deprecated for long enough.

Depends on D10802.

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Subscribers: PiRK

Differential Revision: https://reviews.bitcoinabc.org/D10803