bip174: update changelog for semver/consistency #2145

following up on #2135 (review).

Per https://semver.org/:

Given a version number MAJOR.MINOR.PATCH, increment the:

MAJOR version when you make incompatible API changes
MINOR version when you add functionality in a backward compatible manner
PATCH version when you make backward compatible bug fixes

Per https://keepachangelog.com/en/1.0.0/:

Changelogs are for humans.

Should you ever rewrite a changelog?

Sure. There are always good reasons to improve a changelog.

I am not convinced that a metadata update like a Status advancement warrants a bump of MINOR, also see: #2143 (review)

I think a status update is reasonably significant.

For instance, "Version 1.0.0 is used for promotion to Complete" -- so it arguably doesn't make sense that the other status updates would be patch.