Bump starlette in /examples/fastapi-background-tasks/app (#530)

Bumps [starlette](https://github.com/encode/starlette) from 0.36.3 to 0.40.0.
- [Release notes](https://github.com/encode/starlette/releases)
- [Changelog](https://github.com/encode/starlette/blob/master/docs/release-notes.md)
- [Commits](Kludex/starlette@0.36.3...0.40.0)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

examples/fastapi-background-tasks/app/requirements.txt

@@ -11,7 +11,7 @@ pydantic==2.6.1
 pydantic_core==2.16.2
 requests==2.32.0
 sniffio==1.3.0
-starlette==0.36.3
+starlette==0.40.0
 typing_extensions==4.9.0
 urllib3==2.2.2
 uvicorn==0.27.0.post1