Remove reference to nonexistent npfctl from blacklistd man page

[bcr]

Summary

Since blacklistd was imported from NetBSD, there existed a reference in blacklistd.8 to npfctl.8. This man page does not exist on FreeBSD and it is unlikely that we will have it in the future since we're maintaining our own version of PF. Remove the reference to npfctl.8.

Test Plan

1. Apply the patch
2. Check output of man ./blacklistd.8

[bcr]

Overcome by events, someone else removed the section by now.