remove unused imports

Author: farahats9

sqlmodel/sql/expression.py

@@ -1,6 +1,5 @@
 # WARNING: do not modify this code, it is generated by expression.py.jinja2
 
-import sys
 from datetime import datetime
 from typing import (
     TYPE_CHECKING,
@@ -12,7 +11,6 @@
     Type,
     TypeVar,
     Union,
-    cast,
     overload,
 )
 from uuid import UUID