lib/Kconfig.debug: fix BOOTPARAM_HUNG_TASK_PANIC comment

The comment for CONFIG_BOOTPARAM_HUNG_TASK_PANIC says:

Say N if unsure.

but since commit 9544f9e6947f ("hung_task: panic when there are more than
N hung tasks at the same time"), N is not a valid value for the option,
leading to a warning at build time:

.config:11736:warning: symbol value 'n' invalid for BOOTPARAM_HUNG_TASK_PANIC

as well as an error when given to menuconfig.

Fix the comment to say '0' instead of 'N'.

Link: https://lkml.kernel.org/r/20260106140140.136446-1-tglozar@redhat.com
Fixes: 9544f9e6947f ("hung_task: panic when there are more than N hung tasks at the same time")
Signed-off-by: Tomas Glozar <tglozar@redhat.com>
Reported-by: Johnny Mnemonic <jm@machine-hall.org>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Cc: Li RongQing <lirongqing@baidu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>