net-mgmt/bind_exporter: update to 0.6.1

Maintainer no longer uses FreeBSD and agrees to pass on maintainership.
Take maintainership and modernise port.

Changelog: https://github.com/prometheus-community/bind_exporter/releases/tag/v0.6.1

PR: 272601
MFH: 2023Q3
Approved by: matt@mattmoriarity.com
Reported by: gert@greenie.muc.de

(cherry picked from commit e7cc77abf57583550c560b29c87944071a44dad5)