Removed unnecessary sip import that was causing import errors.

IPython/external/qt_loaders.py

@@ -220,10 +220,6 b' def import_pyqt5():'
 
     from PyQt5 import QtCore, QtSvg, QtWidgets, QtGui
     
-    # Note that import sip must follow other PyQt5 imports for PyQt >5.11
-    # http://pyqt.sourceforge.net/Docs/PyQt5/incompatibilities.html#pyqt-v5-11
-    import sip
-    
     # Alias PyQt-specific functions for PySide compatibility.
     QtCore.Signal = QtCore.pyqtSignal
     QtCore.Slot = QtCore.pyqtSlot