checks: correct the shebang line filtering for python files
As it is, the only related file is docs/test2rst.py, which was covered by **.py.
Not sure if it matters, but most patterns in core tests are for "#!.*?python".
(Though there are a couple "#!.*python" tests.)
doc generated with sphinx. tutorial exported using sphinxedhghttp://hg.piranha.org.ua/sphinxedhg/