Remove structured logging from the logger interface

pkg/log/logger.go

@@ -6,8 +6,6 @@ package log
 // Logger serves as an adapter interface for logger libraries
 // so that dex does not depend on any of them directly.
 type Logger interface {
-	WithField(key string, value interface{}) Logger
-
 	Info(msg string)
 	Warn(msg string)