tests: use /usr/bin/env python for test-status-inprocess.py

everyone else uses it, and the next commit will add a rule for it

tests/test-status-inprocess.py

@@ -1,4 +1,4 b''
-#!/usr/bin/python
+#!/usr/bin/env python
 from __future__ import absolute_import, print_function
 from mercurial.ui import (
     ui,