remove an old ref to persona from appendix

appendix_X_what_to_do_next.asciidoc

@@ -116,15 +116,9 @@ assure yourself that users can only do what they're authorized to?
 Test for Graceful Degradation
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-
-
-What would happen if Persona went down?  Can we at least show an apologetic
+What would happen if our email server goes down?  Can we at least show an apologetic
 error message to our users?
 
-* Tip: one way of simulating Persona being down is to hack your hosts file (at '/etc/hosts' or 'c:\Windows\System32\drivers\etc'). Remember to revert it in
-the test `tearDown`!
-
-* Think about the server side as well as the client side.