build: bump django from 3.2.12 to 3.2.13 in /docs (#7308)

Bumps [django](https://github.com/django/django) from 3.2.12 to 3.2.13.
- [Release notes](https://github.com/django/django/releases)
- [Commits](django/django@3.2.12...3.2.13)

---
updated-dependencies:
- dependency-name: django
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

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

docs/requirements.txt

@@ -19,13 +19,14 @@ charset-normalizer==2.0.12
 click==8.0.4
     # via pip-tools
 codespell==2.1.0
+    # via -r requirements.in
 colorama==0.4.4
     # via sphinx-autobuild
 coverage==6.3.2
     # via -r requirements.in
 datetime==4.4
     # via -r requirements.in
-django==3.2.12
+django==3.2.13
     # via
     #   -r requirements.in
     #   django-classy-tags