tests: fix share test to actually share the repo
"repo2" is clearly meant to be a share from "repo1" but without
sharing bookmarks. However, `hg unshare` was called in the repo, so it
had become completely unrelated and thus not testing what it was
supposed to test.
Differential Revision: https://phab.mercurial-scm.org/D6385
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}