vendor: switch to using go1.11 modules

vendor/google.golang.org/api/option/credentials_notgo19.go

@@ -1,32 +0,0 @@
-// Copyright 2018 Google Inc. All Rights Reserved.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//      http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-// +build !go1.9
-
-package option
-
-import (
-	"golang.org/x/oauth2/google"
-	"google.golang.org/api/internal"
-)
-
-type withCreds google.DefaultCredentials
-
-func (w *withCreds) Apply(o *internal.DialSettings) {
-	o.Credentials = (*google.DefaultCredentials)(w)
-}
-
-func WithCredentials(creds *google.DefaultCredentials) ClientOption {
-	return (*withCreds)(creds)
-}