config: fix example for etcd

This patch fixes iproto.listen and iproto.advertise.peer in local.yaml.

Part of #8862

NO_DOC=changes in example
NO_TEST=will be tested in EE
NO_CHANGELOG=changes in example

doc/examples/config/etcd/local.yaml

@@ -5,6 +5,8 @@ config:
     - http://localhost:2379
 
 iproto:
-  listen: 'unix/:./{{ instance_name }}.iproto'
+  listen:
+    - uri: 'unix/:./{{ instance_name }}.iproto'
   advertise:
-    peer: replicator@
+    peer:
+      login: replicator