www/tt-rss: Update to g20210423 e8f78181f

This update adds a new plugin installer and removes the web based installer.

• Update to g20210423 (e8f78181f).
  • New config.php syntax.
  • Removeal of web installer.
  • New web based plug installer.
• web plugin installer requires git.
• pkg-message changes due to web installer removal.
• ttrssd update to handle database schema upgrades.
• ttrssd use daemon and cleanup.
• UPDATING for config.php changes.
• pkg-plist cleanup.

PR: 255476
Reported by: Derek Schrock (maintainer)
Differential Revision: https://reviews.freebsd.org/D30030