Update pytest-httpx requirement from ~=0.12.0 to ~=0.12.1 (#108)

Updates the requirements on [pytest-httpx](https://github.com/Colin-b/pytest_httpx) to permit the latest version.
- [Release notes](https://github.com/Colin-b/pytest_httpx/releases)
- [Changelog](https://github.com/Colin-b/pytest_httpx/blob/develop/CHANGELOG.md)
- [Commits](Colin-b/pytest_httpx@v0.12.0...v0.12.1)

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

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

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

requirements_dev.txt

@@ -4,4 +4,4 @@ pylint~=2.9
 pytest~=6.2
 pytest-asyncio~=0.15.1
 pytest-cov~=2.12
-pytest-httpx~=0.12.0
+pytest-httpx~=0.12.1