treediscovery: update test expectation
I'm not sure why this needs an update, but the test passes for me both
pure and non-pure.
Differential Revision: https://phab.mercurial-scm.org/D860
https://bz.mercurial-scm.org/1089
$ hg init
$ mkdir a
$ echo a > a/b
$ hg ci -Am m
adding a/b
$ hg rm a
removing a/b (glob)
$ hg ci -m m a
$ mkdir a b
$ echo a > a/b
$ hg ci -Am m
adding a/b
$ hg rm a
removing a/b (glob)
$ cd b
Relative delete:
$ hg ci -m m ../a
$ cd ..