Bump starlette from 0.19.0 to 0.20.4

Bumps [starlette](https://github.com/encode/starlette) from 0.19.0 to 0.20.4.
- [Release notes](https://github.com/encode/starlette/releases)
- [Changelog](https://github.com/encode/starlette/blob/master/docs/release-notes.md)
- [Commits](encode/starlette@0.19.0...0.20.4)

---
updated-dependencies:
- dependency-name: starlette
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

poetry.lock

@@ -7,7 +7,7 @@ license = "MIT"
 
 [tool.poetry.dependencies]
 python = "^3.9"
-starlette = "^0.19.0"
+starlette = "^0.20.4"
 nested_dict = "^1.61"
 uvicorn = {extras = ["standard"], version = "^0.17.6"}
 motor = "3.0.0"