net-mgmt/prometheus2: Direct commit to correct distinfo

When cherry-pick'ing 2.61.1, distinfo was incorrectly merged. This is a
direct commit to 2021Q2 to fix the issue.

Fixes: ece647d08c3933df136bef37559c6987eec192a7
Reported by: phyber (irc), mandree
Approved by: lwhsu (mentor, implicit), portmgr (implicit, fix build)