Ontology: use rdfs:label on dprod:securitySchemaType property

[jgeluk]

Tracks part of #98. Fix typo using rdf:label; should be rdfs:label on dprod:securitySchemaType property. Refs #98

[jgeluk]

Clarification: use rdfs:label on dprod:securitySchemaType

Issue: #139 tracks a typo where the property uses rdf:label instead of rdfs:label.

Current ontology fragment (incorrect):

dprod:securitySchemaType
  a rdf:Property, owl:ObjectProperty ;
  dct:description "The security schema type used for authentication and communication with this Data Service."@en ;
  rdfs:isDefinedBy dprod: ;
  rdfs:domain dcat:DataService ;
  # rdfs:range rdf:resource ; # better let user decide
  rdf:label "security schema type" ;
.

Expected ontology fragment (correct):

dprod:securitySchemaType
  a rdf:Property, owl:ObjectProperty ;
  dct:description "The security schema type used for authentication and communication with this Data Service."@en ;
  rdfs:isDefinedBy dprod: ;
  rdfs:domain dcat:DataService ;
  # rdfs:range rdf:resource ; # better let user decide
  rdfs:label "security schema type" ;
.

Why this matters:

• rdfs:label is the standard annotation for human-readable names defined in RDFS.
• rdf:label is not a defined term in the RDF namespace, so validators and tooling may ignore it.
• Aligns with how other resources in DPROD use labels.

Suggested acceptance criteria:

• Replace rdf:label with rdfs:label on dprod:securitySchemaType in ontology/dprod/dprod-ontology.ttl.
• Rebuild the spec and verify dist/dprod.ttl and site display the correct label.
• Link the PR to close Ontology: use rdfs:label on dprod:securitySchemaType property #139 and reference ontology issues #98.

Refs #98