bpo-40275: Use new test.support helper submodules in tests (GH-21449)

diff --git a/Lib/test/test__opcode.py b/Lib/test/test__opcode.py
index 0fb39ee..3bb64a7 100644
--- a/Lib/test/test__opcode.py
+++ b/Lib/test/test__opcode.py
@@ -1,5 +1,5 @@
 import dis
-from test.support import import_module
+from test.support.import_helper import import_module
 import unittest
 
 _opcode = import_module("_opcode")