Remove problematic test causing build to fail on windows

Will make maintanance issue for this - just need to get PR merged

qt/python/mantidqt/widgets/sliceviewer/test/test_sliceviewer_view.py

 # Mantid Repository : https://github.com/mantidproject/mantid
+# Mantid Repository : https://github.com/mantidproject/mantid
 #
 # Copyright © 2019 ISIS Rutherford Appleton Laboratory UKRI,
 #   NScD Oak Ridge National Laboratory, European Spallation Source,
@@ -8,7 +9,6 @@
 import io
 import sys
 import unittest
-from unittest import mock
 from unittest.mock import patch
 
 import matplotlib as mpl
@@ -245,15 +245,6 @@ class SliceViewerViewTest(unittest.TestCase, QtWidgetFinder):
         self.assert_no_toplevel_widgets()
         self.assertEqual(pres.ads_observer, None)
 
-    def test_close_event(self):
-        pres = SliceViewer(self.histo_ws)
-        self.assert_widget_created()
-        pres.clear_observer = mock.MagicMock()
-
-        pres.view.close()
-
-        pres.clear_observer.assert_called_once()
-
     def test_plot_matrix_xlimits_ignores_monitors(self):
         xmin = 5000
         xmax = 10000