Silence output from noblogs-cron

Fixes issue ai3/prod#198.

roles/noblogs/files/noblogs.cron

 # Run WP cron jobs periodically.
 # We can run as 'root', in-container will set the right user before
 # spawning the command inside the container.
-23 */2 * * * root runcron --name noblogs-cron --splay 3600 -- /usr/local/bin/in-container noblogs-http on-local-blogs run-cron
+# This command is very verbose, so we send its output to /dev/null.
+23 */2 * * * root runcron --name noblogs-cron --no-syslog --splay 3600 -- /usr/local/bin/in-container noblogs-http on-local-blogs run-cron >/dev/null 2>&1
 
 # Wipe the sessions directory - there is a cron job inside the
 # container but until https://git.autistici.org/ai3/docker/mailman/issues/7