Update httpx requirement from ~=0.23.1 to ~=0.23.3

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@0.23.1...0.23.3)

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

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

requirements.txt

@@ -1,5 +1,5 @@
 fastapi~=0.88.0
-httpx~=0.23.1
+httpx~=0.23.3
 hypercorn~=0.14.3
 pydantic~=1.10.4
 pydantic[email]