Make SAML2 configuration match sample config generated using generate command

roles/matrix-synapse/templates/synapse/homeserver.yaml.j2

@@ -1204,7 +1204,7 @@ saml2_config:
   # Instead of putting the config inline as above, you can specify a
   # separate pysaml2 configuration file:
   #
-  #config_path: "CONFDIR/sp_conf.py"
+  #config_path: "/data/sp_conf.py"
 
   # the lifetime of a SAML session. This defines how long a user has to
   # complete the authentication process, if allow_unsolicited is unset.