Update golang dependencies

vendor/google.golang.org/appengine/namespace.go

@@ -1,25 +0,0 @@
-// Copyright 2012 Google Inc. All rights reserved.
-// Use of this source code is governed by the Apache 2.0
-// license that can be found in the LICENSE file.
-
-package appengine
-
-import (
-	"fmt"
-	"regexp"
-
-	"golang.org/x/net/context"
-
-	"google.golang.org/appengine/internal"
-)
-
-// Namespace returns a replacement context that operates within the given namespace.
-func Namespace(c context.Context, namespace string) (context.Context, error) {
-	if !validNamespace.MatchString(namespace) {
-		return nil, fmt.Errorf("appengine: namespace %q does not match /%s/", namespace, validNamespace)
-	}
-	return internal.NamespacedContext(c, namespace), nil
-}
-
-// validNamespace matches valid namespace names.
-var validNamespace = regexp.MustCompile(`^[0-9A-Za-z._-]{0,100}$`)