narrow: remove custom filelog type This functionality is now handled by core as of the previous commit. I wanted this to be a standalone commit because the deleted code makes a reference to remotefilelog's file type missing a node() method and this may have implications to narrow+remotefilelog usage. The code in core doesn't perform this check and therefore behavior may be subtly different and buggy. But I /think/ the check is merely a performance optimization and nothing more. So I'm optimistic this will continue to "just work." Differential Revision: https://phab.mercurial-scm.org/D4644