Bump httpx from 0.27.2 to 0.28.1 in /ci/latest

Bumps [httpx](https://github.com/encode/httpx) from 0.27.2 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@0.27.2...0.28.1)

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

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

Author: dependabot[bot]

ci/latest/requirements.txt

@@ -2,7 +2,7 @@
 # is used in a GitHub Actions workflow to test the compatibility with the
 # latest versions of the dependencies. This file is monitored by Dependabot.
 nextline-graphql==0.7.10
-httpx==0.27.2
+httpx==0.28.1
 pytest-asyncio==0.25.2
 pytest-cov==6.0.0
 pytest-timeout==2.3.1