doc:locking: fix locktorture parameter description

The description was talking about two default values: I removed the
wrong one.

Signed-off-by: Federico Vaga <federico.vaga@vaga.pv.it>
Link: https://lore.kernel.org/r/20191201121941.6971-1-federico.vaga@vaga.pv.it


Signed-off-by: Jonathan Corbet <corbet@lwn.net>