Fixes a bug in persistency of conversations:

CH.END is persited as other states, however CH._update_state expects to completely delete keys once they reach that state. So I now call CH._state_update manually in _initialize_persistence.

Tests still missng.

Reference: https://t.me/pythontelegrambotgroup/707714

• [ ] Added .. versionadded:: NEXT.VERSION, .. versionchanged:: NEXT.VERSION or .. deprecated:: NEXT.VERSION to the docstrings for user facing changes (for methods/class descriptions, arguments and attributes)
• Created new or adapted existing unit tests
• Documented code changes according to the CSI standard <https://standards.mousepawmedia.com/en/stable/csi.html>__
• Added myself alphabetically to AUTHORS.rst (optional)
• [ ] Added new classes & modules to the docs and all suitable __all__ s
• Checked the Stability Policy <https://docs.python-telegram-bot.org/stability_policy.html>_ in case of deprecations or changes to documented behavior