refactor: remove use of boost::algorithm::replace_first
Summary:
This is a backport of core#20067
I remove a trivial comment, to avoid having two comments on the previous lines.
Test Plan: ninja all check-all
Reviewers: #bitcoin_abc, Fabien
Reviewed By: #bitcoin_abc, Fabien
Differential Revision: https://reviews.bitcoinabc.org/D10768