Bump starlette from 0.47.3 to 0.49.1 in /a2a/test-python-a2a-server

Bumps [starlette](https://github.com/Kludex/starlette) from 0.47.3 to 0.49.1.
- [Release notes](https://github.com/Kludex/starlette/releases)
- [Changelog](https://github.com/Kludex/starlette/blob/main/docs/release-notes.md)
- [Commits](Kludex/starlette@0.47.3...0.49.1)

---
updated-dependencies:
- dependency-name: starlette
  dependency-version: 0.49.1
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]