bpo-36710: Fix compiler warning on PyThreadState_Delete() (GH-12962)

_PyThreadState_Delete() has no return value.

Python/pystate.c

@@ -826,7 +826,7 @@ _PyThreadState_Delete(_PyRuntimeState *runtime, PyThreadState *tstate)
 void
 PyThreadState_Delete(PyThreadState *tstate)
 {
-    return _PyThreadState_Delete(&_PyRuntime, tstate);
+    _PyThreadState_Delete(&_PyRuntime, tstate);
 }