Bump mangum from 0.19.0 to 0.20.0

Bumps [mangum](https://github.com/Kludex/mangum) from 0.19.0 to 0.20.0.
- [Release notes](https://github.com/Kludex/mangum/releases)
- [Changelog](https://github.com/Kludex/mangum/blob/main/CHANGELOG.md)
- [Commits](Kludex/mangum@0.19.0...0.20.0)

---
updated-dependencies:
- dependency-name: mangum
  dependency-version: 0.20.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

poetry.lock

@@ -27,7 +27,7 @@ yarl = "^1.18.3"
 pydantic = "^2.12.5"
 asgiref = "^3.11.0"
 eval-type-backport = "^0.3.1"
-mangum = "^0.19.0"
+mangum = "^0.20.0"
 wireup = "^2.2.2"
 python-json-logger = "^4.0.0"
 python-dateutil = "^2.9.0"