Remove a bunch of unused imports (#3323)

stdlib/3/unittest/loader.pyi

@@ -1,4 +1,3 @@
-import sys
 import unittest.case
 import unittest.suite
 import unittest.result

stdlib/3/unittest/result.pyi

@@ -1,4 +1,4 @@
-from typing import Any, List, Optional, Tuple, Type
+from typing import List, Optional, Tuple, Type
 from types import TracebackType
 import unittest.case
 

stdlib/3/unittest/runner.pyi

@@ -1,5 +1,4 @@
 from typing import Callable, Optional, TextIO, Tuple, Type, Union
-import sys
 import unittest.case
 import unittest.result
 import unittest.suite