Update vendor

vendor/github.com/google/renameio/doc.go

@@ -0,0 +1,21 @@
+// Copyright 2018 Google Inc.
+//
+// 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.
+
+// Package renameio provides a way to atomically create or replace a file or
+// symbolic link.
+//
+// Caveat: this package requires the file system rename(2) implementation to be
+// atomic. Notably, this is not the case when using NFS with multiple clients:
+// https://stackoverflow.com/a/41396801
+package renameio