dsession,workermanage: drop handling of pytest_captured_warning

Since d153e0a4c4 the remote doesn't send
events for this hook at all (I think perhaps wrongly, but it's history
by now), so no point in handling it in the coordinator side.

src/xdist/workermanage.py

@@ -374,16 +374,6 @@ class WorkerController:
                     nodeid=kwargs["nodeid"],
                     fslocation=kwargs["nodeid"],
                 )
-            elif eventname == "warning_captured":
-                warning_message = unserialize_warning_message(
-                    kwargs["warning_message_data"]
-                )
-                self.notify_inproc(
-                    eventname,
-                    warning_message=warning_message,
-                    when=kwargs["when"],
-                    item=kwargs["item"],
-                )
             elif eventname == "warning_recorded":
                 warning_message = unserialize_warning_message(
                     kwargs["warning_message_data"]