Generated `pyproject.toml` uses non-standard `poetry` attributes

[micolous]

The generated pyproject.toml file declares all of its attributes using non-standard poetry-specific attributes:

python-client-generator/tests/expected/fastapi_app_client/pyproject.toml

Lines 1 to 5 in 05b2c51

	[tool.poetry]
	name = "fastapi-project"
	version = "0.1.0"
	description = "Autogenerated httpx async client for fastapi-project"
	authors = ["Autogenerated Client <autogenerated@client.com>"]

But per the specification, this should be:

[project]
name = "fastapi-project"
version = "0.1.0"
...

One should be able to use another build tool (such as uv), and the generated package works correctly.