bpo-40275: Use new test.support helper submodules in tests (GH-21785)

diff --git a/Lib/test/test_zipfile64.py b/Lib/test/test_zipfile64.py
index 3a788de..810fded 100644
--- a/Lib/test/test_zipfile64.py
+++ b/Lib/test/test_zipfile64.py
@@ -17,6 +17,7 @@
 
 from tempfile import TemporaryFile
 
+from test.support import os_helper
 from test.support import TESTFN, requires_zlib
 
 TESTFN2 = TESTFN + "2"
@@ -138,8 +139,8 @@
                 self.assertEqual(content, "%d" % (i**3 % 57))
 
     def tearDown(self):
-        support.unlink(TESTFN)
-        support.unlink(TESTFN2)
+        os_helper.unlink(TESTFN)
+        os_helper.unlink(TESTFN2)
 
 if __name__ == "__main__":
     unittest.main()