doc: use serial comma in cluster docs

Refs: nodejs/node#11321
Refs: nodejs/node#17384

PR-URL: nodejs/node#42989
Reviewed-By: Darshan Sen <[email protected]>
Reviewed-By: Rich Trott <[email protected]>
Reviewed-By: Mohammed Keyvanzadeh <[email protected]>

Author: tniessen

doc/api/cluster.md

@@ -746,7 +746,7 @@ primary.
 
 The event handler is executed with two arguments, the `worker` contains the
 worker object and the `address` object contains the following connection
-properties: `address`, `port` and `addressType`. This is very useful if the
+properties: `address`, `port`, and `addressType`. This is very useful if the
 worker is listening on more than one address.
 
 ```js