Remove reference to distributed versions.

We don't distribute mongosniff any more as of 2.6.0.
Related info -
https://jira.mongodb.org/browse/HELP-685
https://groups.google.com/d/msg/mongodb-dev/dmnm0i1g-NE/QCIAZp6nBGQJ

Signed-off-by: kay <kay.kim@10gen.com>