Remove unused imports in test modules.
diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index 1c12252..0404c09 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -31,9 +31,8 @@
 import unittest
 import warnings
 import weakref
-import gc
 import abc
-from itertools import chain, cycle, count
+from itertools import cycle, count
 from collections import deque
 from test import test_support as support