Downgrade Kubernetes vendor version

Multus community decide that multus support the Kubernetes that
Kubernetes community supports, so changed vendor code to the
oldest version of currently supported.

vendor/golang.org/x/sys/unix/ptrace_ios.go

@@ -1,12 +0,0 @@
-// Copyright 2020 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.
-
-//go:build ios
-// +build ios
-
-package unix
-
-func ptrace(request int, pid int, addr uintptr, data uintptr) (err error) {
-	return ENOTSUP
-}