build(deps): bump idna in /docs in the production-dependencies group (#4575)

Bumps the production-dependencies group in /docs with 1 update: [idna](https://github.com/kjd/idna).


Updates `idna` from 3.18 to 3.19
- [Release notes](https://github.com/kjd/idna/releases)
- [Changelog](https://github.com/kjd/idna/blob/master/HISTORY.md)
- [Commits](kjd/idna@v3.18...v3.19)

---
updated-dependencies:
- dependency-name: idna
  dependency-version: '3.19'
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: production-dependencies
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

docs/requirements.txt

@@ -7,7 +7,7 @@ certifi==2026.7.22
 chardet==7.6.0
 commonmark==0.9.2
 docutils==0.20.1
-idna==3.18
+idna==3.19
 imagesize==2.0.0
 myst-parser==5.1.0 
 packaging==26.3