Update sepaxml requirement from ==2.6.* to ==2.7.* (#5431)

Updates the requirements on [sepaxml](https://github.com/raphaelm/python-sepaxml) to permit the latest version.
- [Commits](https://github.com/raphaelm/python-sepaxml/compare/2.6.0...2.7.0)

---
updated-dependencies:
- dependency-name: sepaxml
  dependency-version: 2.7.0
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Raphael Michel <michel@pretix.eu>

pyproject.toml

@@ -92,7 +92,7 @@ dependencies = [
   "reportlab==4.4.*",
   "requests==2.32.*",
   "sentry-sdk==2.42.*",
-  "sepaxml==2.6.*",
+  "sepaxml==2.7.*",
   "stripe==7.9.*",
   "text-unidecode==1.*",
   "tlds>=2020041600",