[3.13] gh-128759: fix data race in type_modified_unlocked (GH-128764) (#128769)

* gh-128759: fix data race in `type_modified_unlocked` (GH-128764)
(cherry picked from commit 6e1e780)

Co-authored-by: sobolevn <mail@sobolevn.me>

Author: miss-islington

Objects/typeobject.c

@@ -996,9 +996,15 @@ type_modified_unlocked(PyTypeObject *type)
        We don't assign new version tags eagerly, but only as
        needed.
      */
+#ifdef Py_GIL_DISABLED
+    if (_Py_atomic_load_uint_relaxed(&type->tp_version_tag) == 0) {
+        return;
+    }
+#else
     if (type->tp_version_tag == 0) {
         return;
     }
+#endif
     // Cannot modify static builtin types.
     assert((type->tp_flags & _Py_TPFLAGS_STATIC_BUILTIN) == 0);