[easy][py] remove unused classes in openai.py (#729)

[easy][py] remove unused classes in openai.py




couple of classes were defined but not used. Tested this by "find all
references" on each class. No results showed up, so its safe to remove
them

## Testplan

<img width="527" alt="Screenshot 2024-01-03 at 12 21 40 PM"
src="https://github.com/lastmile-ai/aiconfig/assets/141073967/33382f79-824c-4b88-975a-b12f09daa379">
<img width="575" alt="Screenshot 2024-01-03 at 12 21 57 PM"
src="https://github.com/lastmile-ai/aiconfig/assets/141073967/f87948fd-324e-4854-b4f9-28861e123f44">
<img width="514" alt="Screenshot 2024-01-03 at 12 22 13 PM"
src="https://github.com/lastmile-ai/aiconfig/assets/141073967/47398fbd-cd78-4f97-b894-f938ef008bda">

python/src/aiconfig/default_parsers/openai.py

@@ -366,24 +366,6 @@ def id(self) -> str:
         return self.model_id
 
 
-class GPT4Parser(DefaultOpenAIParser):
-    def __init__(self):
-        model_id = "gpt-4"
-        super().__init__(model_id)
-
-
-class GPT3TurboParser(DefaultOpenAIParser):
-    def __init__(self):
-        model_id = "gpt-3.5-turbo"
-        super().__init__(model_id)
-
-
-class ChatGPTParser(DefaultOpenAIParser):
-    def __init__(self):
-        model_id = "ChatGPT"
-        super().__init__(model_id)
-
-
 def reduce(acc, delta):
     acc = copy.deepcopy(acc)