build(deps): bump django-stubs-ext from 5.1.2 to 5.1.3

Bumps [django-stubs-ext](https://github.com/typeddjango/django-stubs) from 5.1.2 to 5.1.3.
- [Release notes](https://github.com/typeddjango/django-stubs/releases)
- [Commits](typeddjango/django-stubs@5.1.2...5.1.3)

---
updated-dependencies:
- dependency-name: django-stubs-ext
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>