erofs: do not prompt for risk any more when using big pcluster

The big pcluster feature has been merged for a year, it has been mostly
stable now.

Signed-off-by: Yue Hu <huyue2@coolpad.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20220407050505.12683-1-huyue2@coolpad.com


Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>