FIX: display correct reply count for crawler (PR #10881)

Subtract one from post count for reply count, like what the js app implement. Very tiny change no deserve a special test.

GitHub

CLA assistant check
Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
You have signed the CLA already but the status is still pending? Let us recheck it.

Thanks this seems good.