pre-commit import fixes

Author: gpshead

Lib/test/test_remote_pdb.py

@@ -8,7 +8,6 @@
 import subprocess
 import sys
 import textwrap
-import threading
 import traceback
 import unittest
 import unittest.mock

Lib/test/test_traceback_timestamps/test_basic.py

@@ -1,7 +1,4 @@
-import os
-import sys
 import unittest
-import subprocess
 import re
 from traceback import TIMESTAMP_AFTER_EXC_MSG_RE_GROUP
 

Lib/test/test_warnings/__init__.py

@@ -7,7 +7,6 @@
 import re
 import sys
 import textwrap
-import traceback
 import types
 from typing import overload, get_overloads
 import unittest