fix(router.py): don't cooldown on apiconnectionerrors

Fixes issue where model would be in cooldown due to api connection errors

litellm/llms/vertex_ai.py

@@ -897,7 +897,9 @@ def completion(
     except Exception as e:
         if isinstance(e, VertexAIError):
             raise e
-        raise VertexAIError(status_code=500, message=str(e))
+        raise litellm.APIConnectionError(
+            message=str(e), llm_provider="vertex_ai", model=model
+        )
 
 
 async def async_completion(