uitest: disable the one unreliable math test for now

I still need to research what is going wrong there. It seem to happen when the starting instance
has the startup problem with the active frame.

Change-Id: I903f758dbf02072decf88d5d30c358eb742aeb8e

uitest/math_tests/start.py

@@ -13,6 +13,8 @@ from uitest.framework import UITestCase
 
 from uitest.debug import sleep
 
+import unittest
+
 class SimpleMathTest(UITestCase):
 
     def test_start_math(self):
@@ -61,6 +63,7 @@ class SimpleMathTest(UITestCase):
 
         self.ui_test.close_doc()
 
+    @unittest.skip("on windows the f4 does not always work")
     def test_complete_math(self):
         self.ui_test.create_doc_in_start_center("math")