dns/powerdns: update to 4.2.1

4.2.1 release notes:
This release fixes several bugs and makes a few features more robust or
intuitive. It also contains a few performance improvements for API users.

For a full list of changes look here:
https://doc.powerdns.com/authoritative/changelog/4.2.html#change-4.2.1

PR: 242519
Submitted by: Ralf van der Enden <tremere@cainites.net> (maintainer)