fix lint error

Created using spr 1.3.7

Author: jroelofs

lnt/server/db/migrations/upgrade_18_to_19.py

@@ -7,7 +7,6 @@
 columns following the same column-type rules as upgrade_0_to_1.
 """
 
-import sqlalchemy
 from sqlalchemy import (Boolean, Column, DateTime, Float, ForeignKey, Integer,
                         LargeBinary, String, select)
 from sqlalchemy.orm import sessionmaker