hosts: Decommission k8s-ctrl0

Just a few days before its third birthday 🎂

There are now three Kubernetes control plane nodes:

* _ctrl-2ed8d3.k8s.pyrocufflink.black_ Raspberry Pi CM4
* _ctrl-crave.k8s.pyrocufflink.black_ (virtual machine)
* _ctrl-sycamore.k8s.pyrocufflink.black_ (virtual machine)

hosts

@@ -97,7 +97,6 @@ file0.pyrocufflink.blue
 burp-server
 
 [k8s-controller]
-k8s-ctrl0.pyrocufflink.blue
 ctrl-2ed8d3.k8s.pyrocufflink.black
 
 [k8s-iot-net-ctrl]
@@ -185,7 +184,6 @@ dc-headphone.pyrocufflink.blue
 file0.pyrocufflink.blue
 git0.pyrocufflink.blue
 haproxy0.pyrocufflink.blue
-k8s-ctrl0.pyrocufflink.blue
 loki1.pyrocufflink.blue
 nut1.pyrocufflink.blue
 nvr2.pyrocufflink.blue