Update pillow requirement from ==12.2.* to ==12.3.*

Updates the requirements on [pillow](https://github.com/python-pillow/Pillow) to permit the latest version.
- [Release notes](https://github.com/python-pillow/Pillow/releases)
- [Changelog](https://github.com/python-pillow/Pillow/blob/main/CHANGES.rst)
- [Commits](https://github.com/python-pillow/Pillow/compare/12.2.0...12.3.0)

---
updated-dependencies:
- dependency-name: pillow
  dependency-version: 12.3.0
  dependency-type: direct:production
...

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

pyproject.toml

@@ -77,7 +77,7 @@ dependencies = [
   "paypal-checkout-serversdk==1.0.*",
   "PyJWT==2.13.*",
   "phonenumberslite==9.0.*",
-  "Pillow==12.2.*",
+  "Pillow==12.3.*",
   "pretix-plugin-build",
   "protobuf==7.35.*",
   "psycopg2-binary",