Update starlette requirement

Updates the requirements on [starlette](https://github.com/encode/starlette) to permit the latest version.

Updates `starlette` to 0.41.3
- [Release notes](https://github.com/encode/starlette/releases)
- [Changelog](https://github.com/encode/starlette/blob/master/docs/release-notes.md)
- [Commits](encode/starlette@0.35.0...0.41.3)

---
updated-dependencies:
- dependency-name: starlette
  dependency-type: direct:production
  dependency-group: pip
...

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

backend/requirements.txt

@@ -26,7 +26,7 @@ requests==2.31.0
 rfc3986==1.5.0
 sniffio==1.3.0
 SQLAlchemy==1.4.47
-starlette>=0.35.0,<0.36.0
+starlette>=0.35.0,<0.42.0
 typing==3.7.4.3
 typing-extensions>=4.8.0
 ujson==5.7.0