pyproject.toml follows PEP639 and allows mecab-ko<2.0.0

[martinpopel]

follow https://peps.python.org/pep-0639/
see #284

[Copilot]

Pull request overview

This PR updates the project's pyproject.toml to comply with PEP 639 for license specification and relaxes the mecab-ko dependency constraint.

• Migrates license specification from file reference to SPDX identifier format
• Removes redundant license classifier (now redundant with SPDX identifier)
• Allows mecab-ko versions up to (but not including) 2.0.0 instead of being capped at 1.0.2

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[martinpopel]

@copilot Why are the tests still failing with

ValueError: invalid pyproject.toml config: `project.license`.
      configuration error: `project.license` must be valid exactly by one definition (2 matches found):
      
          - keys:
              'file': {type: string}
            required: ['file']
          - keys:
              'text': {type: string}
            required: ['text']

?

[Copilot]

@martinpopel I've opened a new pull request, #287, to work on those changes. Once the pull request is ready, I'll request review from you.

[martinpopel]

superseded by #287