sw: disable testTableKeep on WNT

Fails from time to time, like so:
https://tinderbox.libreoffice.org/cgi-bin/gunzip.cgi?tree=MASTER&brief-log=1517842001.29090#err2

Change-Id: Ia33193fbfa05da58d31bcc5008beea32c1feb2fe
(cherry picked from commit b2a05316)
Reviewed-on: https://gerrit.libreoffice.org/49289Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

sw/qa/extras/ww8export/ww8export.cxx

@@ -1273,7 +1273,7 @@ DECLARE_WW8EXPORT_TEST(testCommentExport, "comment-export.odt")
     }
 }
 
-#if !defined(MACOSX)
+#if !defined(MACOSX) && !defined(_WIN32)
 #if !TEST_FONTS_MISSING
 DECLARE_WW8EXPORT_TEST(testTableKeep, "tdf91083.odt")
 {