Bump httpx from 0.27.2 to 0.28.0

Bumps [httpx](https://github.com/encode/httpx) from 0.27.2 to 0.28.0.
- [Release notes](https://github.com/encode/httpx/releases)
- [Changelog](https://github.com/encode/httpx/blob/master/CHANGELOG.md)
- [Commits](encode/httpx@0.27.2...0.28.0)

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

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

requirements.txt

@@ -5,7 +5,7 @@ Werkzeug==3.1.3
 bleach==6.2.0
 feedgen==1.0.0
 gunicorn==23.0.0
-httpx==0.27.2
+httpx==0.28.0
 jsonpatch==1.33
 marshmallow==3.23.1
 pytest==8.3.3