Update stripe requirement from ==7.9.* to ==15.3.*

Updates the requirements on [stripe](https://github.com/stripe/stripe-python) to permit the latest version.
- [Release notes](https://github.com/stripe/stripe-python/releases)
- [Changelog](https://github.com/stripe/stripe-python/blob/master/CHANGELOG.md)
- [Commits](https://github.com/stripe/stripe-python/compare/v7.9.0b1...v15.3.1)

---
updated-dependencies:
- dependency-name: stripe
  dependency-version: 15.3.1
  dependency-type: direct:production
...

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

pyproject.toml

@@ -96,7 +96,7 @@ dependencies = [
   "requests==2.34.*",
   "sentry-sdk==2.66.*",
   "sepaxml==2.7.*",
-  "stripe==7.9.*",
+  "stripe==15.3.*",
   "text-unidecode==1.*",
   "tlds>=2026072401",
   "tqdm==4.*",