[validation] Fix REJECT message comments

Summary:
Comments change only.

This is a backport of Core PR17004 [4/5]
Commit https://github.com/bitcoin/bitcoin/pull/17004/commits/04a2f326ec0f06fb4fce1c4f93500752f05dede8
Depends on D8183

Test Plan: ninja

Reviewers: O1 Bitcoin ABC, #bitcoin_abc, deadalnix

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D8184