gh-69605: In test_pyrepl.test_already_imported*, invalidate FS import caches (#143436)

This makes the test robust against file systems with low timestamp resolution, which otherwise would fail to re-import in the tight loop of the test.

Author: ambv

Lib/test/test_pyrepl/test_pyrepl.py

@@ -1192,6 +1192,7 @@ def test_already_imported_module_without_origin_or_spec(self):
                 (dir1 / mod).mkdir()
                 (dir1 / mod / "__init__.py").touch()
                 (dir1 / mod / "foo.py").touch()
+                pkgutil.get_importer(_dir1).invalidate_caches()
                 module = importlib.import_module(mod)
                 assert module.__spec__
                 if mod == "no_origin":