bundle: remove obsolete (and duplicate) comment

Change 1e28ec9744bf (changegroup: move chunk extraction into a
getchunks method of unbundle10, 2014-04-10) extracted some code to a
getchunks() method and copied a comment about the changegroup format
to the new method. The copy that remains in the old place, doesn't
make much sense there, so let's remove it.

mercurial/bundle2.py

@@ -1314,10 +1314,6 b' def writebundle(ui, cg, filename, bundle'
 
     # parse the changegroup data, otherwise we will block
     # in case of sshrepo because we don't know the end of the stream
-
-    # an empty chunkgroup is the end of the changegroup
-    # a changegroup has at least 2 chunkgroups (changelog and manifest).
-    # after that, an empty chunkgroup is the end of the changegroup
     return changegroup.writechunks(ui, chunkiter, filename, vfs=vfs)
 
 @parthandler('changegroup', ('version', 'nbchanges', 'treemanifest'))