util/linuxfw/linuxfwtest: remove unused package (#19520)

Added in 2022, this appears to be unused now.

Updates #cleanup

Signed-off-by: Andrew Lytvynov <awly@tailscale.com>

util/linuxfw/linuxfwtest/linuxfwtest.go

@@ -1,31 +0,0 @@
-// Copyright (c) Tailscale Inc & contributors
-// SPDX-License-Identifier: BSD-3-Clause
-
-//go:build cgo && linux
-
-// Package linuxfwtest contains tests for the linuxfw package. Go does not
-// support cgo in tests, and we don't want the main package to have a cgo
-// dependency, so we put all the tests here and call them from the main package
-// in tests intead.
-package linuxfwtest
-
-import (
-	"testing"
-	"unsafe"
-)
-
-/*
-#include <sys/socket.h>  // socket()
-*/
-import "C"
-
-type SizeInfo struct {
-	SizeofSocklen uintptr
-}
-
-func TestSizes(t *testing.T, si *SizeInfo) {
-	want := unsafe.Sizeof(C.socklen_t(0))
-	if want != si.SizeofSocklen {
-		t.Errorf("sockLen has wrong size; want=%d got=%d", want, si.SizeofSocklen)
-	}
-}

util/linuxfw/linuxfwtest/linuxfwtest_unsupported.go

@@ -1,18 +0,0 @@
-// Copyright (c) Tailscale Inc & contributors
-// SPDX-License-Identifier: BSD-3-Clause
-
-//go:build !cgo || !linux
-
-package linuxfwtest
-
-import (
-	"testing"
-)
-
-type SizeInfo struct {
-	SizeofSocklen uintptr
-}
-
-func TestSizes(t *testing.T, si *SizeInfo) {
-	t.Skip("not supported without cgo")
-}