[backport#16185 3/3] doc: Add release note for the new gettransaction argument

Summary:
https://github.com/bitcoin/bitcoin/pull/16185/commits/9965940e35c445ccded55510348af228ff22f0e9

Depends on D7371

Concludes backport of Core PR16185

Test Plan:

read release notes

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D7372