hosts: remove dns0.p.b

I've moved handling of DNS to the border firewall instead of a dedicated
virtual machine.  Originally, the VM was necessary because the UniFi
Security Gateway sucked and could not (easily) handle the complex
configuration I wanted to use.  Since moving to the new firewall, this
is no longer a problem.

Having DNS on a VM is problematic when full-network outages occur, like
the one that happened on 16 August 2022.  When everything starts back
up, DNS is unavailable.  libvirt VM autostart does not work for machines
that have been migrated between hosts (the auto-start flag is not
migrated, and libvirt "forgets" that the VM was supposed to autostart if
it is migrated away and back).  I plan to script a solution for this at
some point, but I still think it makes more sense for the firewall to
handle it.  It will certainly make it come up quicker regardless.

hosts

@@ -123,7 +123,6 @@ bw0.pyrocufflink.blue
 cloud0.pyrocufflink.blue
 dc0.pyrocufflink.blue
 dc2.pyrocufflink.blue
-dns0.pyrocufflink.blue
 file0.pyrocufflink.blue
 git0.pyrocufflink.blue
 hass2.pyrocufflink.blue
@@ -141,10 +140,8 @@ smtp1.pyrocufflink.blue
 web0.pyrocufflink.blue
 
 [pyrocufflink-dhcp]
-dns0.pyrocufflink.blue
 
 [pyrocufflink-dns]
-dns0.pyrocufflink.blue
 
 [radius:children]
 samba-dc