Drop support for MacOS X Carbon UI

According to Anders Nawroth [1] and list of available downloads [2],
these builds aren't supported any more.

[1] https://github.com/neo4j-contrib/neoclipse/pull/53#issuecomment-27428059
[2] https://github.com/neo4j-contrib/neoclipse/blob/master/README.asciidoc#neoclipse-for-neo4j-191