Downgrade pytest-asyncio to v0.21.1

dev-requirements.txt

@@ -1,7 +1,7 @@
 pytest==8.1.1
 flake8==7.0.0
 pytest-timeout==2.3.1
-pytest-asyncio==0.23.6
+pytest-asyncio==0.21.1
 requests==2.31.0
 httpx==0.24.1 # version 0.24.1 is required by httpx_ws
 httpx_ws==0.4.2