allow building free-threaded wheels on 3.14t

[kumaraditya303]

See #302

This PR allows building free-threaded wheels for tree-sitter-rust which cannot use existing abi3 wheels.

[wetneb]

Since the setup.py file is generated by tree-sitter itself, I am wondering if you have submitted this improvement to https://github.com/tree-sitter/tree-sitter?
Once the change is merged and released there, this repository should probably be updated by re-generating the bindings via tree-sitter itself.
With this method, you'd ensure that many other grammars benefit from your improvement, and that this grammar benefits from all other improvements to the bindings that were accepted in tree-sitter itself.
That being said, this particular grammar is known for not reviewing external PRs very actively, which is why we've started a fork at https://codeberg.org/grammar-orchard/tree-sitter-rust-orchard (which is also uploaded on PyPI). I'd be happy to regenerate bindings there if needed.