Follow up of #7674


Mobility DCAT theme vocabulary top concepts is available at
https://mobilitydcat-ap.github.io/controlled-vocabularies/mobility-theme/latest/index.html#/

The vocabulary contains 2 top concepts:

```xml
<skos:hasTopConcept rdf:resource="https://w3id.org/mobilitydcat-ap/mobility-theme/data-content-category"/>
<skos:hasTopConcept rdf:resource="https://w3id.org/mobilitydcat-ap/mobility-theme/data-content-sub-category"/>
```
which are not really needed for browsing the main categories and sub categories.

Use the narrower terms of the "content category" top concept as the top concepts of the scheme
to facilitate keyword selection in editor and generate proper facet hierarchy in search.

The 2 default top concepts of the vocabulary are replaced by correct one.