py-pyqt4: fix for the depends_lib reset caused by the Python PortGroup

[Joshua Root]

On 2016-12-18 03:59 , Marko Käning wrote:
> René, I missed this double and now even triple dependency to qt4-mac completely.
>
> Josh, which stub port do you mean? dbus-python##? If so, why is it unneeded and why had it been there before already.

py-pyqt4 is the stub port.

> What do you suggest to recover from this mess?

I would revert the last commit and remove port:qt4-mac from the 
depends_lib-append on line 82.

- Josh