[PATCH 1 of 2] discovery: fix a typo in a comment

[Pierre-Yves David]

# HG changeset patch
# User Pierre-Yves David <pierre-yves.david at fb.com>
# Date 1444430225 25200
#      Fri Oct 09 15:37:05 2015 -0700
# Node ID bfde4c287d34ea09716861af2fd63e38f27439fb
# Parent  6e715040c1725b5debce888c4f7d3fdbf55cc900
# EXP-Topic disc.cleanup
discovery: fix a typo in a comment

The idea here is that the code is imperfect, not that it is impossible to get
something behaving properly.

diff --git a/mercurial/discovery.py b/mercurial/discovery.py
--- a/mercurial/discovery.py
+++ b/mercurial/discovery.py
@@ -306,11 +306,11 @@ def checkheads(repo, remote, outgoing, r
         discardedheads = set()
         if repo.obsstore:
             # remove future heads which are actually obsoleted by another
             # pushed element:
             #
-            # XXX as above, There are several cases this case does not handle
+            # XXX as above, There are several cases this code does not handle
             # XXX properly
             #
             # (1) if <nh> is public, it won't be affected by obsolete marker
             #     and a new is created
             #