Removed shapeless from Scala 2, since it is fully replaced by Magnolia

[soujiro32167]

This is not bin-compat, since the shapeless library is gone. This seems fine, since the removed values were implicits, and this will be a minor version bump

[soujiro32167]

@ayoub-benali please review

[vlovgr]

This will have to wait until at least v2.0.0 since it breaks binary compatibility (it removes public definitions). There might still be library users who rely on having Shapeless Coproduct support, so we shouldn't remove it before the next major version.