tests: adapt now that Mercurial clears the merge state for empty wdir
`hg evolve` forgot to clear the merge state when its attempt to commit
resulted in no commit because the working copy had no changes. That
resulted in test-evolve-issue5967.t showing a conflict state that
shouldn't be there. The responsibility for clearing the merge state
was moved into Mercurial in Mercurial in 6a34e438461b (commit: clear
resolved mergestate even if working copy is clean, 2020-02-28), so the
bug is now fixed in `hg evolve`, which impacts that test case.
CORE-TEST-OUTPUT-UPDATE: 6a34e438461b
#require test-repoEnableobsolescencetoavoidthewarningissuewhenobsmarkerarefound$cat<<EOF>>$HGRCPATH>[diff]>git=yes>[experimental]>evolution=all>EOFGobackinthehgrepo$cd$TESTDIR/..$fornodein`hglog--rev'not public() and ::. and not desc("# no-check-commit")'--template'{node|short}\n'`;do>hgexport$node|${RUNTESTDIR}/../contrib/check-commit>${TESTTMP}/check-commit.out>if[$?-ne0];then>echo"Revision $node does not comply with rules">echo'------------------------------------------------------'>cat${TESTTMP}/check-commit.out>echo>fi>done