⬆ Update httpx requirement from <0.26.0,>=0.15.5 to >=0.15.5,<0.28.0

Updates the requirements on [httpx](https://github.com/encode/httpx) to permit the latest version.
- [Release notes](https://github.com/encode/httpx/releases)
- [Changelog](https://github.com/encode/httpx/blob/master/CHANGELOG.md)
- [Commits](encode/httpx@0.15.5...0.27.0)

---
updated-dependencies:
- dependency-name: httpx
  dependency-type: direct:production
...

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

requirements.txt

@@ -1,6 +1,6 @@
 PyGithub
 pydantic>=2.0.0
 pydantic-settings
-httpx>=0.15.5,<0.26.0
+httpx>=0.15.5,<0.28.0
 email-validator
 Jinja2