fix: correct typo in event name for handoff occurrence

Author: Rehan-Ul-Haq

src/agents/_run_impl.py

@@ -720,7 +720,7 @@ def stream_step_result_to_queue(
             elif isinstance(item, HandoffCallItem):
                 event = RunItemStreamEvent(item=item, name="handoff_requested")
             elif isinstance(item, HandoffOutputItem):
-                event = RunItemStreamEvent(item=item, name="handoff_occured")
+                event = RunItemStreamEvent(item=item, name="handoff_occurred")
             elif isinstance(item, ToolCallItem):
                 event = RunItemStreamEvent(item=item, name="tool_called")
             elif isinstance(item, ToolCallOutputItem):