Update dependencies

vendor/github.com/DataDog/zstd/zstd_ddict.h

@@ -1,6 +1,5 @@
-#ifndef USE_EXTERNAL_ZSTD
 /*
- * Copyright (c) Meta Platforms, Inc. and affiliates.
+ * Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
  * All rights reserved.
  *
  * This source code is licensed under both the BSD-style license (found in the
@@ -16,7 +15,7 @@
 /*-*******************************************************
  *  Dependencies
  *********************************************************/
-#include "zstd_deps.h"   /* size_t */
+#include <stddef.h>   /* size_t */
 #include "zstd.h"     /* ZSTD_DDict, and several public functions */
 
 
@@ -43,5 +42,3 @@ void ZSTD_copyDDictParameters(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict);
 
 
 #endif /* ZSTD_DDICT_H */
-
-#endif /* USE_EXTERNAL_ZSTD */