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.
bundle: avoid crash when no good changegroup version found
When using treemanifests, only changegroup3 bundles can be
created. However, there is currently no way of requesting a
changegroup3 bundle, so we run into an assertion in
changegroup.getbundler() when trying to get a changroup2
bundler. Let's avoid the traceback and print a short error message
instead.