update firewall information for efm (#6390)

* update firewall information for efm

This updates the firewall prereqs text to make it clear that:
1) the port that needs to be open is the one used with the bind.address property
2) the admin.port port doesn't need to be opened.

* change "command line process" to "utility"

We use the word "utility" in other places, which looks a lot better.

product_docs/docs/efm/4/installing/prerequisites.mdx

@@ -79,7 +79,7 @@ If a Linux firewall (that is, iptables) is enabled on the host of a Failover Man
 /sbin/service iptables save
 ```
 
-This command opens the port 7800. Failover Manager connects by way of the port that corresponds to the port specified in the cluster properties file.
+This command opens the port 7800. Failover Manager connects by way of the port that corresponds to the port specified by `bind.address` in the cluster properties file. The port specified by `admin.port` does not need to be open. It is only used for local communication when the `efm` utility is run.
 
 ## Ensure that the database user has sufficient privileges