filelog: stop proxying start(), end(), and length() (API)
These were needed by the censoring code, which formerly lived in the
censor extension. Now that there is a censoring API on the file storage
interface, nothing uses these methods and we can stop proxying them.
Differential Revision: https://phab.mercurial-scm.org/D4657
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}