Update typing.Union and types.UnionType definitions for 3.14

[Viicos]

As per python/cpython#105511.

[srittau]

Thanks for contributing! Unfortunately, as outlined in our CONTRIBUTING document we only accept pull requests to the standard library for future Python versions after the first beta version has been released. This is in part to prevent churn in the stubs, and in part because the testing infrastructure for the future version is not yet in place. Please feel free to open a new PR when the first beta version has been released. Alternatively, if this PR is still relevant, you can leave a comment here to reopen it.

[Avasam]

@Viicos Beta 1 has been released! I don't think contributors can re-open their PRs. You can let us know if you'd like us to re-open this or you can create a new PR!

[Viicos]

Yes happy to have this one reopened.

[JelleZijlstra]

I tried this too but ran into some trouble with how type checkers are special-casing these symbols; might need some changes inside type checkers too.

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉