Bump httpx from 0.24.1 to 0.26.0

Bumps [httpx](https://github.com/encode/httpx) from 0.24.1 to 0.26.0.
- [Release notes](https://github.com/encode/httpx/releases)
- [Changelog](https://github.com/encode/httpx/blob/master/CHANGELOG.md)
- [Commits](encode/httpx@0.24.1...0.26.0)

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

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

requirements_test.txt

@@ -2,4 +2,4 @@ pytest==7.4.2
 pytest-cov==4.1.0
 pytest-timeout==2.1.0
 # tests require sub-dependencies of starlette
-httpx==0.24.1
+httpx==0.26.0