tests: avoid grafting the same change over and over The test case added in a1381eea7c7d (graft: do not use `.remove` on a smart set (regression), 2014-04-28) added a test case that grafted the same change (renaming 'a' to 'b') three times over. It had description "graft works on complex revset", but AFACT, all that it cared about was that some ancestor of the working copy was in the set of revisions to graft. So this patch changes the test to do that instead. (I plan to later make it so that grafting these renames on top of each won't create the empty commits they currently create.) Differential Revision: https://phab.mercurial-scm.org/D7804