Bump httpx in /{{cookiecutter.project_slug}}/backend

Bumps [httpx](https://github.com/encode/httpx) from 0.24.1 to 0.27.2.
- [Release notes](https://github.com/encode/httpx/releases)
- [Changelog](https://github.com/encode/httpx/blob/master/CHANGELOG.md)
- [Commits](encode/httpx@0.24.1...0.27.2)

---
updated-dependencies:
- dependency-name: httpx
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

{{cookiecutter.project_slug}}/backend/poetry.lock

@@ -22,7 +22,7 @@ black = "^23.10.1"
 pytest = "^7.4.3"
 ipython = "^8.16.1"
 pytest-cov = "^4.1.0"
-httpx = "^0.24.1"
+httpx = "^0.28.1"
 pytest-asyncio = "^0.21.1"
 
 [build-system]