net/hblock: Update to 3.1.0

Update from v2.1.7 to v3.1.0 (skipped v3.0.0 and v.3.0.1).

Changelog: https://github.com/hectorm/hblock/compare/v2.1.7...v3.1.0

PR: 251311
Submitted by: Lewis Cook <vulcan@wired.sh> (maintainer)
Approved by: arrowd (mentor)
Differential Revision: https://reviews.freebsd.org/D27322