doc: Remove comments that just repeat what the code does

Summary:
No need to artificially bloat the code and waste space.

This is a partial backport of core#28060
https://github.com/bitcoin/bitcoin/pull/28060/commits/fa8d227d58f7baa5a9be1b88930f4813bf6eedb1

Depends on D18980

Test Plan: NA

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D18981