net-p2p/tremotesf: update to 2.5.0

Remove separate distfile for libtremotesf as it has been merged into
main tree.

Remove separate distfile for cpp-httplib as we can use www/cpp-httplib
now.

Note: despite Qt 6 support added, we can't use it right now as KDE
Framework 6 is also needed.

Release info: https://github.com/equeim/tremotesf2/releases/tag/2.5.0

PR: 274511