Fix test_canvas_reinit.

The figure is no longer set stale because `resize` is no longer called.
There's no reason the figure should be stale until it's ready to be
drawn, but we don't really need a whole main loop for this test.

Author: QuLogic

lib/matplotlib/tests/test_backend_qt.py

@@ -271,4 +271,5 @@ def crashing_callback(fig, stale):
     fig.stale_callback = crashing_callback
     # this should not raise
     canvas = FigureCanvasQTAgg(fig)
+    fig.stale = True
     assert called