Fix typo in long-term memory documentation

Author: Fengrui-Liu

docs/content/6.memory/3.long-term-memory.md

@@ -28,7 +28,7 @@ session_id = "..."
 new_session_id = "..."
 
 long_term_memory = LongTermMemory(backend=...)  # default backend is `opensearch`
-agent = Agent(long_term_memory=long_term_memory) # agent with long term memort backend
+agent = Agent(long_term_memory=long_term_memory) # agent with long term memory backend
 
 runner = Runner(
     agent=agent,