tests: fix test-check-module-imports.t broken by D9150

Differential Revision: https://phab.mercurial-scm.org/D9177

tests/test-doctest.py

@@ -4,7 +4,7 b' from __future__ import absolute_import'
 from __future__ import print_function
 
 import doctest
-import os.path
+import os
 import re
 import subprocess
 import sys