fixup: fix test after merge: this sequence should be truly unorderable - experiment 3

Author: victor-nexthop

src/pytest_order/plugin.py

@@ -2,7 +2,8 @@
 
 import pytest
 from _pytest.config import Config
-from pytest import Mark, Function, Parser, Session
+from _pytest.mark import Mark
+from pytest import Function, Parser, Session
 
 from .sorter import Sorter