safesocket: remove the IPN protocol support

Updates #6417

Change-Id: I78908633de842d83b2cc8b10a864a0f88ab1b113
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

version/export_test.go

@@ -0,0 +1,15 @@
+// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package version
+
+var (
+	ExportParse          = parse
+	ExportFindModuleInfo = findModuleInfo
+	ExportCmdName        = cmdName
+)
+
+type (
+	ExportParsed = parsed
+)