Do not suggest "doer" as a replacement for "slave"

"Doer" is mentioned in the dictionary either in combination with "of",
e.g. "a doer of good", or with the meaning of "an active and energetic
person".

Thus the suggested replacement for "slave" does not match the dictionary
definition of the word and is prone to misunderstanding. Suggest "node"
instead, as a less specific version of "control plane node" which is already
in the text.

content/language/word-list.md

@@ -44,7 +44,7 @@ These recommendations are broken into two groups. The preferred group does not u
 Preferred: 
 
 * Control plane/control plane node
-* Controller/doer
+* Controller/node
 * Primary/replica
 * Primary/secondary