Bump idna from 3.4 to 3.6 in /docs (#165)

Bumps [idna](https://github.com/kjd/idna) from 3.4 to 3.6.
- [Changelog](https://github.com/kjd/idna/blob/master/HISTORY.rst)
- [Commits](kjd/idna@v3.4...v3.6)

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

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

docs/requirements.txt

@@ -7,7 +7,7 @@ certifi==2024.2.2
 chardet==5.2.0
 commonmark==0.9.1
 docutils==0.20.1
-idna==3.4
+idna==3.6
 imagesize==1.4.1
 pytz==2024.1
 recommonmark==0.7.1