Bump idna from 3.6 to 3.7 in /doc (ufs-community#1071)

Bumps [idna](https://github.com/kjd/idna) from 3.6 to 3.7.
- [Release notes](https://github.com/kjd/idna/releases)
- [Changelog](https://github.com/kjd/idna/blob/master/HISTORY.rst)
- [Commits](kjd/idna@v3.6...v3.7)

---
updated-dependencies:
- dependency-name: idna
  dependency-type: indirect
...

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

doc/requirements.txt

@@ -18,7 +18,7 @@ docutils==0.20.1
  # sphinx
  # sphinx-rtd-theme
  # sphinxcontrib-bibtex
-idna==3.6
+idna==3.7
  # via requests
 imagesize==1.4.1
  # via sphinx