chore(deps): update twine requirement from ==5.* to ==6.*

Updates the requirements on [twine](https://github.com/pypa/twine) to permit the latest version.
- [Release notes](https://github.com/pypa/twine/releases)
- [Changelog](https://github.com/pypa/twine/blob/main/docs/changelog.rst)
- [Commits](pypa/twine@5.0.0...6.0.1)

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

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

requirements-testing.txt

@@ -6,4 +6,4 @@ pytest-cov == 6.*
 pytest-xdist == 3.*
 ruff == 0.8.*
 types-pyyaml == 6.*
-twine == 5.*
+twine == 6.*