Rename CheckIfBanned() to MaybeDiscourageAndDisconnect()
Summary:
This completes backport of core PR19219.
This renaming part was previously skipped from D7146 due to missing
backports:
https://reviews.bitcoinabc.org/D7146?id=22789#inline-42357
Test Plan:
ninja all check-all
Reviewers: #bitcoin_abc, PiRK
Reviewed By: #bitcoin_abc, PiRK
Differential Revision: https://reviews.bitcoinabc.org/D8791