net/krill: Update to Version 0.13.1

The Krill UI includes a CA selection dropdown in case you have multiple CAs.
This dropdown used to have a scrollbar, which accidentally got lost
in the UI overhaul we did in version 0.13.0. This is now fixed (#1071)

Changelog: https://github.com/NLnetLabs/krill/releases/tag/v0.13.1

PR: 271822