phabsend: print the actual URL with --confirm
Sometimes people have multiple Phabricator endpoints set in multiple repos.
It seems better for `--confirm` to prompt about the Phabricator endpoint
patches being sent to.
Differential Revision: https://phab.mercurial-scm.org/D513
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}