UITest_writer_tests5: disable unstable test_tdf123378_print_sets_modified()

See <https://gerrit.libreoffice.org/#/c/67754/3> for discussion, the
stability of this test has to be improved before it can be enabled
again.

Change-Id: Iae7d16c7a6c3659de132e2d64ca43865081b3c9b
Reviewed-on: https://gerrit.libreoffice.org/72724Reviewed-by: Miklos Vajna <vmiklos@collabora.com>
Tested-by: Jenkins

sw/qa/uitest/writer_tests5/tdf123378.py

@@ -10,6 +10,8 @@ from uitest.framework import UITestCase
 
 class tdf123378(UITestCase):
    def test_tdf123378_print_sets_modified(self):
+        # FIXME unstable test
+        return
         self.ui_test.create_doc_in_start_center("writer")
         document = self.ui_test.get_component()
         xWriterDoc = self.xUITest.getTopFocusWindow()