veyron2/ipc/model.go: Remove method argument from Lookup

This change removes the 'method' argument from the Dispatcher's Lookup
method. It is not used anywhere in a non-trivial way and we don't have
any plan to use it for anything.

Change-Id: I56910d1e863b90b14a800bafb91e46819c3a7fe6
diff --git a/tools/profile/impl_test.go b/tools/profile/impl_test.go
index e24fb92..1dd149d 100644
--- a/tools/profile/impl_test.go
+++ b/tools/profile/impl_test.go
@@ -79,7 +79,7 @@
 	return &dispatcher{}
 }
 
-func (d *dispatcher) Lookup(suffix, method string) (interface{}, security.Authorizer, error) {
+func (d *dispatcher) Lookup(suffix string) (interface{}, security.Authorizer, error) {
 	return repository.ProfileServer(&server{suffix: suffix}), nil, nil
 }