QT: AA_ShareOpenGLContexts

Makes this go away:
"Qt WebEngine seems to be initialized from a plugin. Please set Qt::AA_ShareOpenGLContexts using QCoreApplication::setAttribute before constructing QGuiApplication."

gui/qt/__init__.py

@@ -92,6 +92,7 @@ class ElectrumGui:
         #network.add_jobs([DebugMem([Abstract_Wallet, SPV, Synchronizer,
         #                            ElectrumWindow], interval=5)])
         QtCore.QCoreApplication.setAttribute(QtCore.Qt.AA_X11InitThreads)
+        QtCore.QCoreApplication.setAttribute(QtCore.Qt.AA_ShareOpenGLContexts)
         self.config = config
         self.daemon = daemon
         self.plugins = plugins