net-im/mastodon: Update 4.3.6 => 4.6.3, take maintainership

Changelog:
https://github.com/mastodon/mastodon/blob/v4.6.3/CHANGELOG.md

Improve port:

• Update WWW - old url redirects to new.
• Replace RM in post-extract with EXTRACT_AFTER_ARGS.

PR: 296573
Sponsored by: UNIS Labs
Co-authored-by: Vladimir Druzenko <vvd@FreeBSD.org>