Update OpenCVDetectPython.cmake

On my MacOS the output of the sphinx-build binary is the following:

Error: Insufficient arguments.

Sphinx v1.2b1
Usage: /usr/local/bin/sphinx-build [options] sourcedir outdir [filenames...]

...

I have installed sphinx, but without this change HAVE_SPHINX==0 for me, so I can't build docs.
Removed useless .*
Merge pull request #1216 from alekcac:sphinx