chore(tests/asgi): mark httpx as incompatible with py314

Author: vytas7

requirements/tests

@@ -6,7 +6,9 @@ testtools
 
 # ASGI Specific (Daphne & Hypercorn are installed in their own tox env)
 aiofiles
-httpx
+# NOTE(vytas): httpcore (a dependency of httpx) fails to import under 3.14.0a6:
+#   https://github.com/encode/httpcore/issues/994
+httpx; python_version < '3.14'
 uvicorn >= 0.17.0
 websockets >= 13.1