ci: make lint workflow check pyproject.toml

[anakin87]

Related Issues

When changing dependencies, the lint workflow (including mypy) should run appropriately to find type issues.
This did not happen, for example, in #9178.

Proposed Changes:

• make the lint workflow also monitor pyproject.toml

How did you test it?

I tested this in this PR, triggering lint with a change to pyproject.toml. Mypy ran: https://github.com/deepset-ai/haystack/actions/runs/14353439800/job/40237681508

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test: and added ! in case the PR includes breaking changes.
• I documented my code
• I ran pre-commit hooks and fixed any issue

[coveralls]

Pull Request Test Coverage Report for Build 14353439800

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.03%) to 90.371%

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Totals
Change from base Build 14350711803:	0.03%
Covered Lines:	10652
Relevant Lines:	11787

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💛 - Coveralls

[sjrl]

Looks good!