[backport#15730 4/4] doc: Add release notes for 15730

Summary:
https://github.com/bitcoin/bitcoin/pull/15730/commits/b6c748f84909212dce73e4b77aa125ed1e108a10

Depends on D7012

Concludes backport of Core PR15730

Test Plan:

read it

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D7013