scripts: Remove 'max-silent-time' from the default options.

scripts: Remove 'max-silent-time' from the default options.

Fixes <http://bugs.gnu.org/27157>.

Having a finite default `max-silent-time' value for scripts such as 'guix
environment' could lead to timeouts when building subtitutes; this was
undesirable.

This change also fixes client behavior to match the documentation, which
is that by default the daemon's settings are honored.

* guix/scripts/archive.scm (%default-options): Remove max-silent-time entry.
* guix/scripts/copy.scm (%default-options): Likewise.
* guix/scripts/environment.scm (%default-options): Likewise.
* guix/scripts/pack.scm (%default-options): Likewise.
* guix/scripts/package.scm (%default-options): Likewise.
* guix/scripts/pull.scm (%default-options): Likewise.
* guix/scripts/system.scm (%default-options): Likewise.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>