zstd: Remove no-pthread patch used for building with mcfgthreads

Evidentially upstream has improved their feature detection so we no
longer need this patch.

CC @lhmouse

pkgs/tools/compression/zstd/default.nix

@@ -22,9 +22,7 @@ stdenv.mkDerivation rec {
 
   patches = [
     ./playtests-darwin.patch
-  ] # This I didn't upstream because if you use posix threads with MinGW it will
+  ];
-    # work fine, and I'm not sure how to write the condition.
-    ++ lib.optional stdenv.hostPlatform.isWindows ./mcfgthreads-no-pthread.patch;
 
   postPatch = lib.optionalString (!static) ''
     substituteInPlace build/cmake/CMakeLists.txt \

pkgs/tools/compression/zstd/mcfgthreads-no-pthread.patch

@@ -1,13 +0,0 @@
-diff --git a/programs/Makefile b/programs/Makefile
-index 7882fe8c..1e8237bb 100644
---- a/programs/Makefile
-+++ b/programs/Makefile
-@@ -107,7 +107,7 @@ HAVE_THREAD := $(shell [ "$(HAVE_PTHREAD)" -eq "1" -o -n "$(filter Windows%,$(OS
- ifeq ($(HAVE_THREAD), 1)
- THREAD_MSG := ==> building with threading support
- THREAD_CPP := -DZSTD_MULTITHREAD
--THREAD_LD := -pthread
-+THREAD_LD :=
- else
- THREAD_MSG := $(NO_THREAD_MSG)
- endif