Remove duplicated license in pyproject.toml

[lin826]

Summary

Resolve the building issue from pyproject.toml

22:32:47   | ValueError: invalid pyproject.toml config: `project.license`.
22:32:47   | configuration error: `project.license` must be valid exactly by one definition (2 matches found):
22:32:47   |
22:32:47   |     - keys:
22:32:47   |         'file': {type: string}
22:32:47   |       required: ['file']
22:32:47   |     - keys:
22:32:47   |         'text': {type: string}
22:32:47   |       required: ['text']
22:32:47   |
22:32:47   | WARNING: exit code 1 from a shell command.
22:32:47   NOTE: recipe python3-starlette-0.39.0-r0: task do_compile: Failed

Reference: https://packaging.python.org/en/latest/guides/writing-pyproject-toml/#license

Checklist

• [x] I understand that this PR may be closed in case there was no previous discussion. (This doesn't apply to typos!)
• [ ] I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• [ ] I've updated the documentation accordingly.

[trim21]

I don't think we should remove classifiers? project.license is not right but project.classifiers is still valid.

[Kludex]

Closing this given this was already brought up in uvicorn: https://github.com/encode/uvicorn/pull/1734

But thanks for the PR 🙏