Bug#839567: rake does not work with jruby

[tony mancill]

I agree with Helmut's suggestion that jruby should drop the Provides.
Even if there are contexts in which jruby could act as a ruby
interpreter, I don't think we should encourage our users to use it
when we have ruby available.  Or put another way, if you're using
jruby, it typically to solve a specific problem or because you have
special considerations about your runtime environment, not because
you're looking for a general purpose Ruby interpreter.

If there are no objections, I'll prepare an upload of jruby that drops
the Provides of ruby-interpreter.