Fix sysvinit Sidekiq logging

Now that bin/background_jobs always logs to both standard output and log/sidekiq.log, we are spamming sysvinit users because our init script does not suppress the Sidekiq process's standard output.

We can just use > to redirect here because bin/background_jobs already redirects standard error to standard output.

See #344576 (closed). Caused by !72016 (merged).