fix flake8 lint check failures

Author: lstein

invokeai/app/services/model_records/model_records_sql.py

@@ -42,7 +42,6 @@
 
 import json
 import sqlite3
-import threading
 from pathlib import Path
 from typing import List, Optional, Union
 

tests/app/services/model_records/test_model_records_sql.py

@@ -2,7 +2,6 @@
 Test the refactored model config classes.
 """
 
-import sys
 from hashlib import sha256
 
 import pytest