Bump dnspython from 2.5.0 to 2.6.1 in /tools/pr_checker (#1985)

Bumps [dnspython](https://github.com/rthalley/dnspython) from 2.5.0 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@v2.5.0...v2.6.1)

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

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

tools/pr_checker/requirements.txt

@@ -1,2 +1,2 @@
 click==8.1.7
-dnspython==2.5.0
+dnspython==2.6.1