vendor: update all dependencies to latest versions

vendor/cloud.google.com/go/spanner/not_go18.go

@@ -0,0 +1,23 @@
+// Copyright 2017 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 !go1.8
+
+package spanner
+
+import "google.golang.org/api/option"
+
+// OpenCensus only supports go 1.8 and higher.
+
+func openCensusOptions() []option.ClientOption { return nil }