hgweb: do not audit URL path as working-directory path
Since hgweb is an interface to repository data, we don't need to prohibit
any paths conflicting within the filesystem. Still an access to working
files is audited by filectx.
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}