Reduce console output in sample crontab/systemd service files.

As borgmatic will log to syslog in the sample crontab/systemd service
files, this makes console output redundant. (cron will mail any console
output to the root user; systemd will log any console output to syslog.)

This adds --verbosity -1 to both files to reduce console output to the
minimum.

sample/cron/borgmatic

@@ -1,3 +1,3 @@
 # You can drop this file into /etc/cron.d/ to run borgmatic nightly.
 
-0 3 * * * root PATH=$PATH:/usr/bin:/usr/local/bin /root/.local/bin/borgmatic --syslog-verbosity 1
+0 3 * * * root PATH=$PATH:/usr/bin:/usr/local/bin /root/.local/bin/borgmatic --verbosity -1 --syslog-verbosity 1