Replace some confusing text about "IPFW being loaded/not being loaded/blah"

with some more relevent and clear text about using rc.conf to load the
firewall.

PR		99336
Discussed with:	keramida (follow up to PR, etc.)

en_US.ISO8859-1/books/handbook/firewalls/chapter.sgml

@@ -2228,9 +2228,7 @@ options    IPV6FIREWALL_DEFAULT_TO_ACCEPT</programlisting>
     <sect2 id="firewalls-ipfw-rc">
       <title><filename>/etc/rc.conf</filename> Options</title>
 
-      <para>If you do not have IPFW compiled into your kernel you will
-	need to load it with the following statement in your
-	<filename>/etc/rc.conf</filename>:</para>
+      <para>Enable the firewall:</para>
 
       <programlisting>firewall_enable="YES"</programlisting>