net-p2p/{lib,r}torrent: Roll back to 0.16.5

Due to instability of 0.16.6, roll back to 0.16.5 stable.
As a temporary measure as upstream is working on a release fix, let's
roll back with a portrevision bump.

PR: 292914
Reported by: glebius
Reviewed by: glebius, novel
MFH: 2026Q1
See also: https://github.com/rakshasa/rtorrent/issues/1689

(cherry picked from commit 73e88b9f23d4986b5862933ff0d07f9ebf0aeee7)