Update vendor files to point to kubernetes-1.12.0-beta.1

vendor/golang.org/x/oauth2/twitch/twitch.go

@@ -0,0 +1,19 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package twitch provides constants for using OAuth2 to access Twitch.
+package twitch // import "golang.org/x/oauth2/twitch"
+
+import (
+	"golang.org/x/oauth2"
+)
+
+// Endpoint is Twitch's OAuth 2.0 endpoint.
+//
+// For more information see:
+// https://dev.twitch.tv/docs/authentication
+var Endpoint = oauth2.Endpoint{
+	AuthURL:  "https://id.twitch.tv/oauth2/authorize",
+	TokenURL: "https://id.twitch.tv/oauth2/token",
+}