unbound.conf: Do not set defaults explicitly

unbound.conf: Do not set defaults explicitly

In order to keep configuration files small and easy to review/audit,
omitting defaults makes more sense than configure them explicitly (have
changed my mind here).

Unbound comes with a good default confiuration, and we should only make
changes when they are necessary. In addition, this patch updates the
documentation's URL to the current one.

Signed-off-by: Peter Müller <peter.mueller@ipfire.org>
Cc: Michael Tremer <michael.tremer@ipfire.org>
Reviewed-by: Michael Tremer <michael.tremer@ipfire.org>
Signed-off-by: Arne Fitzenreiter <arne_f@ipfire.org>