wallet: Remove confusing double return value ret+success

Summary:
Also, remove redundant comments

This is a backport of core#19320 [1/2]
https://github.com/bitcoin/bitcoin/pull/19320/commits/fa021e9a5b7e930a3db0febb416942dea3a90a8f

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Subscribers: majcosta

Differential Revision: https://reviews.bitcoinabc.org/D9982