Bump starlette from 0.38.1 to 0.40.0

Bumps [starlette](https://github.com/encode/starlette) from 0.38.1 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](encode/starlette@0.38.1...0.40.0)

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

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