remove unused exception, we return None when there is no data

Author: purificant

src/bubble_data_api_client/exceptions.py

@@ -13,10 +13,6 @@ class BubbleHttpError(BubbleError):
     """Base class for all high level HTTP errors."""
 
 
-class BubbleNotFoundError(BubbleHttpError):
-    """Raised when a resource is not found."""
-
-
 class BubbleUnauthorizedError(BubbleHttpError):
     """Raised when the user is not authorized to access a resource."""