Remove RO-Crate Conversion from Specification

[floWetzels]

The current specification contains a paragraph describing the conversion to RO-Crate as well as a superficial version of the ARC RO-Crate profile: https://github.com/nfdi4plants/ARC-specification/blob/main/ARC%20specification.md#appendix-conversion-of-arcs-to-ro-crates

However, this specification has been moved to a separate repository: https://github.com/nfdi4plants/arc-ro-crate-profile

To prevent inconsistencies, to ease maintenance and to have a unique reference for the profile and process, it would be beneficial to remove the duplication in the ARC specification.

@muehlhaus @HLWeil

[HLWeil]

I think this is a good opportunity to discuss renaming this repository to ARC-Scaffold-specification, @muehlhaus @chgarth?

On the Readme we could state that this specification exclusively describes the Scaffold representation, link the arc-rdm.org for explanations and the newly created ARC-RO-Crate-profile as the specification for the RO-Crate representation.