Remove Named interface (#26913)

`Named` is implemented by every `Method` and future implementations
should implement the method too.

services/auth/interface.go

@@ -27,10 +27,7 @@ type Method interface {
 	// Second argument returns err if verification fails, otherwise
 	// First return argument returns nil if no matched verification condition
 	Verify(http *http.Request, w http.ResponseWriter, store DataStore, sess SessionStore) (*user_model.User, error)
-}
 
-// Named represents a named thing
-type Named interface {
 	Name() string
 }