Remove todo from nrepl version string

[benjamin-asdf]

In describe session we return some TODO strings.
Maybe just something like v1? BTW it doesn't break anything.

context:
clojure-emacs/cider#3467

[borkdude]

The version can be obtained from package.json

[borkdude]

Actually we already have a version constant somewhere, which is also used when you start a REPL, etc.