[api] Bump h11 from 0.14.0 to 0.16.0 in /backend

Bumps [h11](https://github.com/python-hyper/h11) from 0.14.0 to 0.16.0.
- [Commits](python-hyper/h11@v0.14.0...v0.16.0)

---
updated-dependencies:
- dependency-name: h11
  dependency-version: 0.16.0
  dependency-type: indirect
...

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

Author: dependabot[bot]