Update httpx requirement from ~=0.24.1 to ~=0.25.0 in /.dev

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@0.24.1...0.25.0)

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

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

.dev/requirements_dev.txt

@@ -1,5 +1,5 @@
 dulwich~=0.21.6
-httpx~=0.24.1
+httpx~=0.25.0
 invoke~=2.2
 pre-commit>=2.21.0,<3; python_version<"3.8"
 pre-commit~=3.4; python_version>="3.8"