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

mercurial/filelog.py

@@ -214,15 +214,6 b' class filelog(object):'
 
         return self._revlog.clone(tr, destrevlog._revlog, **kwargs)
 
-    def start(self, rev):
-        return self._revlog.start(rev)
-
-    def end(self, rev):
-        return self._revlog.end(rev)
-
-    def length(self, rev):
-        return self._revlog.length(rev)
-
     def compress(self, data):
         return self._revlog.compress(data)