Fix customize notification example

Author: jschaedl

notifier.rst

@@ -500,10 +500,10 @@ very high and the recipient has a phonenumber::
                 && $recipient instanceof AdminRecipient
                 && null !== $recipient->getPhone()
             ) {
-                return ['sms', 'email'];
+                return ['sms'];
             }
 
-            return 'email';
+            return ['email'];
         }
     }