net-p2p/tremotesf: update to 2.6.2

Add compiler:c++20-lang to USES.

Changelog: https://github.com/equeim/tremotesf2/releases/tag/2.6.2

PR: 278274
Approved by: Submitter is maintainer, diizzy (mentor)
Differential Revision: https://reviews.freebsd.org/D44981