Stabilize timetable DST abbreviation test

test/timetable-region-timezone.test.js

@@ -332,7 +332,7 @@ test('timetable timezone abbreviation changes across daylight saving boundaries'
     {
       value: '<p>{{start.tz("Europe/London")}}</p>',
       timetable_group_id: 1,
-      display_mode: 'both',
+      display_mode: 'all',
       max_items: 10
     },
     {