verify: update comment to say that lfs doesn't need fulltext to check renames

The reason is that `filelog.renamed()` indirectly calls `filelog.revision()`,
which is what accesses the full text.  However, LFS wraps `filelog.renamed()`
and completely handles the case where an LFS blob is in play by using rawdata.

I've got a test to demonstrate that this is the case, and prevent regressions.
But the `skipread` flag is set on all lfs revisions when using `--no-lfs`,
regardless of whether or not the blobs are local.  Just above this, that flag is
consulted, causing the rename checks to be skipped.  That will need to be
loosened up first.

Differential Revision: https://phab.mercurial-scm.org/D7709

mercurial/verify.py

@@ -565,8 +565,9 b' class verifier(object):'
 
                 # check renames
                 try:
-                    # This requires resolving fulltext (at least on revlogs). We
-                    # may want ``verifyintegrity()`` to pass a set of nodes with
+                    # This requires resolving fulltext (at least on revlogs,
+                    # though not with LFS revisions). We may want
+                    # ``verifyintegrity()`` to pass a set of nodes with
                     # rename metadata as an optimization.
                     rp = fl.renamed(n)
                     if rp: