filelog: drop _generaldelta attribute (API)
With changegroup moving to emitrevisions(), this revlog-specific
attribute is no longer used and can be deleted. Good riddance.
Differential Revision: https://phab.mercurial-scm.org/D4727
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}