[3.14] pythongh-144601: Use _testmultiphase instead of _testsinglephase in test_importlib (pythonGH-144769)

Author: ZeroIntensity

Lib/test/test_importlib/util.py

@@ -15,7 +15,7 @@
 import tempfile
 import types
 
-_testsinglephase = import_helper.import_module("_testsinglephase")
+import_helper.import_module("_testmultiphase")
 
 
 BUILTINS = types.SimpleNamespace()