Switch to hard-coded Qt5 matplotlib backend

Mixing Qt4/Qt5 could be dangerous in the same process

scripts/MultiPlotting/navigation_toolbar.py

@@ -5,7 +5,7 @@
 #   Institut Laue - Langevin & CSNS, Institute of High Energy Physics, CAS
 # SPDX - License - Identifier: GPL - 3.0 +
 from qtpy import QtGui
-from matplotlib.backends.backend_qt4agg import NavigationToolbar2QT as NavigationToolbar
+from matplotlib.backends.backend_qt5agg import NavigationToolbar2QT as NavigationToolbar
 
 
 class myToolbar(NavigationToolbar):