chore(deps): bump idna from 3.7 to 3.15 in /docs (#6074)

Bumps [idna](https://github.com/kjd/idna) from 3.7 to 3.15.
- [Release notes](https://github.com/kjd/idna/releases)
- [Changelog](https://github.com/kjd/idna/blob/master/HISTORY.md)
- [Commits](https://github.com/kjd/idna/compare/v3.7...v3.15)

---
updated-dependencies:
- dependency-name: idna
  dependency-version: '3.15'
  dependency-type: indirect
...

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

docs/requirements.txt

@@ -19,7 +19,7 @@ docutils==0.20.1
     #   sphinx
 furo==2024.1.29
     # via -r requirements.in
-idna==3.7
+idna==3.15
     # via requests
 imagesize==1.4.1
     # via sphinx