Discounts: Fix incorrect test for subevent date limitation

If two discounts match the same products, the first one wins. Therefore,
the one we want to win in the test must always come last, otherwise the
test is not actually testing anything. In this case, this is highlighted
by the fact that the test does not pass in diffrent orders of discounts
unless we subtract a second from the date, because we compare with <=,
not <.

src/tests/base/test_pricing_discount.py

@@ -1071,11 +1071,11 @@ def test_subevent_date_from(event, item, subevent):
 @scopes_disabled()
 def test_subevent_date_until(event, item, subevent):
     subevent_date = subevent.date_from  # prevent test timing errors
-    d1 = Discount(event=event, condition_min_count=2, benefit_discount_matching_percent=20,
-                  subevent_date_until=subevent_date + timedelta(days=1))
+    d1 = Discount(event=event, condition_min_count=2, benefit_discount_matching_percent=50,
+                  subevent_date_until=subevent_date - timedelta(seconds=1))
     d1.save()
-    d2 = Discount(event=event, condition_min_count=2, benefit_discount_matching_percent=50,
-                  subevent_date_until=subevent_date)
+    d2 = Discount(event=event, condition_min_count=2, benefit_discount_matching_percent=20,
+                  subevent_date_until=subevent_date + timedelta(days=1))
     d2.save()
 
     # (item_id, subevent_id, subevent_date_from, line_price_gross, is_addon_to, is_bundled, voucher_discount)