fix(proxy/utils.py): return different exceptions if key is invalid vs. expired

https://github.com/BerriAI/litellm/issues/1230

litellm/proxy/hooks/parallel_request_limiter.py

@@ -6,6 +6,7 @@ from litellm.integrations.custom_logger import CustomLogger
 from fastapi import HTTPException
 
 class MaxParallelRequestsHandler(CustomLogger): 
+    user_api_key_cache = None
     # Class variables or attributes
     def __init__(self):
         pass