doc: use serial comma in dgram docs

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

PR-URL: nodejs/node#43191
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Mohammed Keyvanzadeh <[email protected]>
Reviewed-By: Rich Trott <[email protected]>

Author: tniessen

doc/api/dgram.md

@@ -214,7 +214,7 @@ added: v0.1.99
 * Returns: {Object}
 
 Returns an object containing the address information for a socket.
-For UDP sockets, this object will contain `address`, `family` and `port`
+For UDP sockets, this object will contain `address`, `family`, and `port`
 properties.
 
 This method throws `EBADF` if called on an unbound socket.