build: Drop ZeroMQ patch for Mingw-w64 < 4.0

The Mingw-w64 5.0 (Ubuntu 18.04 Bionic) is used to build the Windows
binaries now.

depends/patches/zeromq/0001-fix-build-with-older-mingw64.patch

@@ -1,30 +0,0 @@
-From f6866b0f166ad168618aae64c7fbee8775d3eb23 Mon Sep 17 00:00:00 2001
-From: mruddy <6440430+mruddy@users.noreply.github.com>
-Date: Sat, 30 Jun 2018 09:44:58 -0400
-Subject: [PATCH] fix build with older mingw64
-
----
- src/windows.hpp | 7 +++++++
- 1 file changed, 7 insertions(+)
-
-diff --git a/src/windows.hpp b/src/windows.hpp
-index 6c3839fd..2c32ec79 100644
---- a/src/windows.hpp
-+++ b/src/windows.hpp
-@@ -58,6 +58,13 @@
- #include <winsock2.h>
- #include <windows.h>
- #include <mswsock.h>
-+
-+#if defined __MINGW64_VERSION_MAJOR && __MINGW64_VERSION_MAJOR < 4
-+// Workaround for mingw-w64 < v4.0 which did not include ws2ipdef.h in iphlpapi.h.
-+// Fixed in mingw-w64 by 9bd8fe9148924840d315b4c915dd099955ea89d1.
-+#include <ws2def.h>
-+#include <ws2ipdef.h>
-+#endif
- #include <iphlpapi.h>
- 
- #if !defined __MINGW32__
--- 
-2.17.1
-