Improve Assistants intro in README

Author: alexrudall

README.md

@@ -663,9 +663,9 @@ client.finetunes.list_events(id: fine_tune_id)
 
 ### Assistants
 
-Assistants can call models to interact with threads and use tools to perform tasks (see [Assistant Overview](https://platform.openai.com/docs/assistants/overview)).
+Assistants are stateful actors that can have many conversations and use tools to perform tasks (see [Assistant Overview](https://platform.openai.com/docs/assistants/overview)).
 
-To create a new assistant (see [API documentation](https://platform.openai.com/docs/api-reference/assistants/createAssistant)):
+To create a new assistant:
 
 ```ruby
 response = client.assistants.create(