Remove unnecessary Qt signal connection.

QuLogic · QuLogic · commit 26fbd92763c5 · 2018-06-24T16:21:04.000-04:00
This fails with PyQt5.11, but is also unnecessary. `_destroying` is set
to True before this signal is connected, so the callback simply returns
immediately. Thus, just remove the connection entirely.
diff --git a/lib/matplotlib/backends/backend_qt5.py b/lib/matplotlib/backends/backend_qt5.py
@@ -671,7 +671,6 @@ def destroy(self, *args):
         if self.window._destroying:
             return
         self.window._destroying = True
-        self.window.destroyed.connect(self._widgetclosed)
         if self.toolbar:
             self.toolbar.destroy()
         self.window.close()
