Docs: improve readability in WebSocket middleware documentation

tests/test_ws_router.py

@@ -235,7 +235,7 @@ def test_depend_validation():
 
 def test_depend_err_middleware():
     """
-    Verify that it is possible to write custom WebSocket middleware to catch errors
+    Verify that custom WebSocket middleware can catch errors
     """
 
     @websocket_middleware