Remove Distribution from Header

[Sveino]

Summary

When converting between TriG / JSON-LD and CIMXML, the handling of dcat:Distribution should only be in the manifest instance file.

Current behaviour

During conversion from TriG → CIMXML, we observe dataset metadata such as:
<rdf:type rdf:resource="http://www.w3.org/ns/dcat#Distribution"/>
and
<dcterms:issued>2025-02-14T12:00:00+00:00</dcterms:issued>
There is two instance in the export - this is refereting to the one with time.

The TriG file include:

            dcat:distribution  [ rdf:type    dcat:Distribution;
                                 dct:issued  "2025-02-14T12:00:00Z"^^xsd:dateTime
                               ];

This is based on an old specification.

Neider TriG nor CIMXML should include dcat:distribution.