docs(fields): fix link to union modes

[antoni-jamiolkowski]

Change Summary

The description of the union_mode parameter of the Field function is provided with a link to a nonexistent paragraph on the Standard Library Types page: https://docs.pydantic.dev/latest/api/standard_library_types/#union-mode

I believe that the correct link is: https://docs.pydantic.dev/latest/concepts/unions/#union-modes. It has been changed in this PR.

Related issue number

There is none.

Checklist

• The pull request title is a good summary of the changes - it will be used in the changelog
• Unit tests for the changes exist
• Tests pass on CI
• Documentation reflects the changes where applicable
• My PR is ready to review, please add a comment including the phrase "please review" to assign reviewers

[codspeed-hq]

CodSpeed Performance Report

Merging #9431 will not alter performance

_{Comparing antoni-jamiolkowski:docs-change (8892d16) with main (1ea2116)}

Summary

✅ 13 untouched benchmarks

[sydney-runkle]

Looks great, thanks!

[sydney-runkle]

We're working on a fix for the typing extensions tests, and will merge this once that's fixed!

[sydney-runkle]

@antoni-jamiolkowski,

Could you please pull in the changes from main? That should allow tests to pass. Thanks!

[antoni-jamiolkowski]

@sydney-runkle,

Sure 🙂