dependency: (deps): bump httpx from 0.28.0 to 0.28.1 in /backend (#439)

Bumps [httpx](https://github.com/encode/httpx) from 0.28.0 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@0.28.0...0.28.1)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

backend/requirements.txt

@@ -23,7 +23,7 @@ exceptiongroup==1.2.2
 fonttools==4.55.1
 h11==0.14.0
 httpcore==1.0.7
-httpx==0.28.0
+httpx==0.28.1
 idna==3.10
 inflection==0.5.1
 kiwisolver==1.4.7