Tweak glossary definition for Node

The services (eg kubelet) that run on a Node are not the kind of
Service that the Kubernetes API knows about. Reword accordingly.

Also, highlight that Docker is one container runtime and that
there are others.

content/en/docs/reference/glossary/node.md

@@ -14,5 +14,4 @@ tags:
 
 <!--more--> 
 
-A worker machine may be a VM or physical machine, depending on the cluster. It has the {{< glossary_tooltip text="Services" term_id="service" >}} necessary to run {{< glossary_tooltip text="Pods" term_id="pod" >}} and is managed by the master components. The {{< glossary_tooltip text="Services" term_id="service" >}} on a node include Docker, kubelet and kube-proxy.
-
+A worker node may be a VM or physical machine, depending on the cluster. It has local daemons or services necessary to run {{< glossary_tooltip text="Pods" term_id="pod" >}} and is managed by the master components. The daemons on a node include {{< glossary_tooltip text="kubelet" term_id="kubelet" >}}, kube-proxy, and a container runtime such as {{< glossary_tooltip term_id="docker" >}}.