This test was intended to verify that updates from remote B can't
interfere with updates from remote A even if remote B maliciously sets
the same collection ID as remote A. However, the commits intended to
protect against this turned out to have nasty side effects and need to
be reverted.[1] A subsequent commit will revert the use of
OSTREE_REPO_PULL_FLAGS_MIRROR which means this attack is not exploitable
(since refs will be resolved using a refspec which includes the remote
name), at the cost of not supporting more than one remote having the
same collection ID configured. Since we don't support that, it doesn't
make sense to keep this unit test.
Also, the test seems to be failing.
[1] https://github.com/flatpak/flatpak/issues/3215
e467695549
