Python dependency: Bump dnspython from 2.3.0 to 2.6.1 in /web/regression

Bumps [dnspython](https://github.com/rthalley/dnspython) from 2.3.0 to 2.6.1.
- [Release notes](https://github.com/rthalley/dnspython/releases)
- [Changelog](https://github.com/rthalley/dnspython/blob/main/doc/whatsnew.rst)
- [Commits](rthalley/dnspython@v2.3.0...v2.6.1)

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

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

web/regression/requirements.txt

@@ -27,4 +27,4 @@ testtools==2.7.1
 traceback2==1.4.0
 selenium==4.10.0
 # Pinned for https://github.com/eventlet/eventlet/issues/805
-dnspython==2.3.0
+dnspython==2.6.1