Update fluxbb to the latest commit with PHP 8 compatibility, fix
permissions being to strict so http can't access it and rate limit
searching.

The gitdirs are just clones of public repos and don't seem to contain
anything sensitive but better safe than sorry.

Thanks to Christian Rebischke <chris@shibumi.dev>

The location block should also execute PHP otherwise we will just reply
with PHP files.

someone has made a conky script that hits the rss feed every second, so nginx
now limits that to once per minute, returning 503 instead at other times. a
burst is also in place to prevent genuine users being blocked.