L2SS-541: fix linting

tangostationcontrol/tangostationcontrol/toolkit/retriever.py

@@ -8,7 +8,6 @@ from sqlalchemy import create_engine, and_
 from sqlalchemy.orm import sessionmaker
 from sqlalchemy.orm.exc import NoResultFound
 import importlib
-import numpy
 
 class Retriever(ABC):
     """