Remove unnecessary no_af_vsock patch (#839)

In `pyconfig.undefs.h` we have undefined `HAVE_LINUX_VM_SOCKETS_H`, and
based on that, `Modules/socketmodule.h` already undefines `AF_VSOCK` for
us.

cpython/patches/0003-no_af_vsock.patch

@@ -1,22 +0,0 @@
-From 9597e7b2ec30968fe9aec0c5a3bc1187e45bc870 Mon Sep 17 00:00:00 2001
-From: Michael Droettboom <mdboom@gmail.com>
-Date: Sun, 5 Jul 2020 17:39:02 +0200
-Subject: [PATCH] no_af_vsock
-
-
-diff --git a/Modules/socketmodule.h b/Modules/socketmodule.h
-index dff1f8f4e9..6014853ac8 100644
---- a/Modules/socketmodule.h
-+++ b/Modules/socketmodule.h
-@@ -154,6 +154,8 @@ typedef int socklen_t;
- extern "C" {
- #endif
- 
-+#undef AF_VSOCK
-+
- /* Python module and C API name */
- #define PySocket_MODULE_NAME    "_socket"
- #define PySocket_CAPI_NAME      "CAPI"
--- 
-2.25.1
-