Remove unused MFA interface (#25525)

server/einterfaces/mfa.go

@@ -1,15 +0,0 @@
-// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
-// See LICENSE.txt for license information.
-
-package einterfaces
-
-import (
-	"github.com/mattermost/mattermost/server/public/model"
-)
-
-type MfaInterface interface {
-	GenerateSecret(user *model.User) (string, []byte, *model.AppError)
-	Activate(user *model.User, token string) *model.AppError
-	Deactivate(userID string) *model.AppError
-	ValidateToken(secret, token string) (bool, *model.AppError)
-}