Log Message:
py-cachetools: updated to 4.2.4

v4.2.4 (2021-09-30)
- Add submodule shims for backward compatibility.

v4.2.3 (2021-09-29)
- Add documentation and tests for using ``TTLCache`` with
  ``datetime``.
- Link to typeshed typing stubs.
- Flatten package file hierarchy.