Fix JsonFormatter when --profile is attempted

When the `--profile` option is passed to the JsonFormatter it attempts to
run `dump_profile` and output profile information. I believe this is
an error stemming from it's creation as a copy+paste from the
`BaseTextFormatter` and has never worked. (see commits
[[1]](https://github.com/rspec/rspec-core/commit/972591b7b874361686882bdc59b97222c45da8ac)
[[2]](https://github.com/rspec/rspec-core/commit/dcfaa67b6886869e6fcb2878ca5e5a1c6e825806)
)

In RSpec 3, thanks to #1039, this will work, but for 2-14 we should just
kill the bug.