bpo-40645: Fix reference leak in the _hashopenssl extension (GH-26072)

The `PyModule_AddObjectRef` function doesn't steal a reference, so an extra `Py_DECREF` is needed.

Automerge-Triggered-By: GH:tiran

Modules/_hashopenssl.c

@@ -2109,6 +2109,7 @@ hashlib_init_constructors(PyObject *module)
     if (PyModule_AddObjectRef(module, "_constructors", proxy) < 0) {
         return -1;
     }
+    Py_DECREF(proxy);
     return 0;
 }