RFE: use `zoneinfo` instead of `pytz`

[kloczek]

Switch to standard zoneinfo module. Below may help https://github.com/pydantic/pydantic-core/commit/fd262933

[tkloczko@pers-jacek lexicon-3.17.0]$ grep -r pytz
poetry.lock:pytz = {version = ">=2015.7", markers = "python_version < \"3.9\""}
poetry.lock:pytz = ">=2016.10"
poetry.lock:name = "pytz"
poetry.lock:    {file = "pytz-2023.3.post1-py2.py3-none-any.whl", hash = "sha256:ce42d816b81b68506614c11e8937d3aa9e41007ceb50bfdcb0749b921bf646c7"},
poetry.lock:    {file = "pytz-2023.3.post1.tar.gz", hash = "sha256:7b4fddbeb94a1eba4b557da24f19fdf9db575192544270a9101d8509f9f43d7b"},
poetry.lock:name = "types-pytz"
poetry.lock:description = "Typing stubs for pytz"
poetry.lock:    {file = "types-pytz-2023.3.1.1.tar.gz", hash = "sha256:cc23d0192cd49c8f6bba44ee0c81e4586a8f30204970fc0894d209a6b08dab9a"},
poetry.lock:    {file = "types_pytz-2023.3.1.1-py3-none-any.whl", hash = "sha256:1999a123a3dc0e39a2ef6d19f3f8584211de9e6a77fe7a0259f04a524e90a5cf"},
poetry.lock:pytz = "*"
pyproject.toml:types-pytz = "*"

[adferrand]

pytz is not used directly in lexicon code. I remove the reference to types-pytz for mypy.