doc:networking: Fix default value (icmp_ignore_bogus_error_responses).

This patch fixes icmp_ignore_bogus_error_responses default value to be 1 instead
of FALSE. It is initialized to 1 in icmp_sk_init().

Signed-off-by: Rami Rosen <ramirose@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>