sfx2: Drop duplicate MACOSX check

There since:

    commit e103887c8c
    Date:   Fri Jan 11 11:07:23 2013 +0200

        QUARTZ is equivalent to MACOSX

Change-Id: I34d04913af45c529e01249a5f1a9c5f66b7260b4
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/173454
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>

sfx2/source/dialog/filedlghelper.cxx

@@ -1292,7 +1292,7 @@ void FileDialogHelper_Impl::preExecute()
 
     implInitializeFileName( );
 
-#if !(defined(MACOSX) && defined(MACOSX)) && !defined(_WIN32)
+#if !defined(MACOSX) && !defined(_WIN32)
     // allow for dialog implementations which need to be executed before they return valid values for
     // current filter and such