Bump httpx from 0.27.0 to 0.28.1

Bumps [httpx](https://github.com/encode/httpx) from 0.27.0 to 0.28.1.
- [Release notes](https://github.com/encode/httpx/releases)
- [Changelog](https://github.com/encode/httpx/blob/master/CHANGELOG.md)
- [Commits](encode/httpx@0.27.0...0.28.1)

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

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

Author: dependabot[bot]

requirements.txt

@@ -5,4 +5,4 @@ cryptography >= 40.0.0
 pyOpenSSL >= 23.1.1
 asn1==2.7.0
 cattrs >= 23.1.2
-httpx==0.27.0
+httpx==0.28.1