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

[Joshua Root]

<https://github.com/macports/macports-ports/commit/6982d654f53f45585e157ece80ee3ed698cc5d33>

Before this change:

% port deps py\*-pyqt4
Full Name: py-pyqt4 @4.11.4_4
Build Dependencies:   pkgconfig
Library Dependencies: py27-pyqt4
--
Full Name: py27-pyqt4 @4.11.4_4
Build Dependencies:   pkgconfig
Library Dependencies: qt4-mac, python27, py27-sip, qt4-mac, dbus-python27
--
Full Name: py34-pyqt4 @4.11.4_4
Build Dependencies:   pkgconfig
Library Dependencies: qt4-mac, python34, py34-sip, qt4-mac, dbus-python34
--
Full Name: py35-pyqt4 @4.11.4_4
Build Dependencies:   pkgconfig
Library Dependencies: qt4-mac, python35, py35-sip, qt4-mac, dbus-python35

Afterwards:

% port deps py\*-pyqt4
Full Name: py-pyqt4 @4.11.4_4
Build Dependencies:   pkgconfig
Library Dependencies: py27-pyqt4, qt4-mac
--
Full Name: py27-pyqt4 @4.11.4_4
Build Dependencies:   pkgconfig
Library Dependencies: qt4-mac, python27, qt4-mac, py27-sip, qt4-mac,
                       dbus-python27
--
Full Name: py34-pyqt4 @4.11.4_4
Build Dependencies:   pkgconfig
Library Dependencies: qt4-mac, python34, qt4-mac, py34-sip, qt4-mac,
                       dbus-python34
--
Full Name: py35-pyqt4 @4.11.4_4
Build Dependencies:   pkgconfig
Library Dependencies: qt4-mac, python35, qt4-mac, py35-sip, qt4-mac,
                       dbus-python35

This adds a (second) duplicate dependency to the subports and an 
unneeded one to the stub port.

- Josh