Bump httpx from 0.27.2 to 0.28.1

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:development
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

Diff for: poetry.lock

@@ -106,7 +106,7 @@ starlette = ">=0.26.1,<0.45.0"
 strict-rfc3339 = "^0.7"
 webob = "*"
 mypy = "^1.2"
-httpx = ">=0.24,<0.28"
+httpx = ">=0.24,<0.29"
 deptry = ">=0.11,<0.21"
 aiohttp = "^3.8.4"
 pytest-aiohttp = "^1.0.4"