test-import.t: use proper revset order

This test, written after 3.0, is relying on addset being enforced ascending if
both side are ascending. We are about to restore the ordering to 2.9 behavior
(elements are ordered in the order they are specified). We fix the test before
fixing the order.

tests/test-import.t

@@ -1428,7 +1428,7 b' Importing multiple failing patches:'
   $ echo 'B' > b # just to make another commit
   $ hg commit -m "a new base"
   created new head
-  $ hg export --rev 'desc("extended jungle") + desc("four")' | hg import --partial -
+  $ hg export --rev 'desc("four") + desc("extended jungle")' | hg import --partial -
   applying patch from stdin
   patching file a
   Hunk #1 FAILED at 0