Pin black version to ^23.12.0 for CI consistency

pyproject.toml

@@ -36,7 +36,7 @@ pytest-asyncio = "^0.21.1"
 pytest-cov = "^4.1.0"
 httpx = "^0.25.2"
 ruff = "^0.1.6"
-black = "^23.11.0"
+black = "^23.12.0"
 mypy = "^1.7.1"
 
 [tool.black]