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>