chore(deps): update dnspython requirement in /api

Updates the requirements on [dnspython](https://github.com/rthalley/dnspython) to permit the latest version.
- [Release notes](https://github.com/rthalley/dnspython/releases)
- [Changelog](https://github.com/rthalley/dnspython/blob/main/doc/whatsnew.rst)
- [Commits](https://github.com/rthalley/dnspython/compare/v2.5.0...v2.6.1)

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

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

api/requirements.txt

@@ -9,7 +9,7 @@ django-celery-email~=3.0.0
 django-netfields~=1.3.2
 django-pgtrigger~=4.11.0
 django-prometheus~=2.3.1
-dnspython~=2.5.0
+dnspython~=2.6.1
 httpretty~=1.0.5  # 1.1 breaks tests. Does not run in production, so stick to it.
 pyotp~=2.9.0
 psycopg~=3.1.18