Bump pytest-asyncio from 0.23.7 to 0.23.8 in /testbed

Bumps [pytest-asyncio](https://github.com/pytest-dev/pytest-asyncio) from 0.23.7 to 0.23.8.
- [Release notes](https://github.com/pytest-dev/pytest-asyncio/releases)
- [Commits](pytest-dev/pytest-asyncio@v0.23.7...v0.23.8)

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

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

testbed/pyproject.toml

@@ -12,7 +12,7 @@ test = [
     "fonttools==4.53.1 ; sys.platform == 'linux'",
     "pillow==9.2.0",
     "pytest==8.3.1",
-    "pytest-asyncio==0.23.7",
+    "pytest-asyncio==0.23.8",
 ]
 
 [tool.briefcase]