Use PyVarObject_HEAD_INIT instead PyObject_HEAD_INIT

--- a/tlshmodule.cpp
+++ b/tlshmodule.cpp
@@ -59,7 +59,7 @@
 #include <Python.h>
 #include <new>
 #include <bytesobject.h>
-#include "tlsh.h"
+#include <tlsh/tlsh.h>

 // to generate the "T1" hashes introduced in TLSH 4.0.0
 // see 4.0.0 from 26/Mar/2020 at https://github.com/trendmicro/tlsh/blob/master/Change_History.md
@@ -286,10 +286,7 @@ static PyGetSetDef Tlsh_getsetters[] = {
 };

 static PyTypeObject tlsh_TlshType = {
-    PyObject_HEAD_INIT(NULL)
-#if PY_MAJOR_VERSION < 3
-    0,                         /* ob_size */
-#endif
+    PyVarObject_HEAD_INIT(NULL, 0)
     "tlsh.Tlsh",               /* tp_name */
     sizeof(tlsh_TlshObject),   /* tp_basicsize */
     0,                         /* tp_itemsize */