Check RDF and schema URLs for v3.0.1 spec and model

[bact]

In spec and in model, if https://spdx.org/... URL is available for a resource, should use that one:

• JSON context https://spdx.org/rdf/3.0.1/spdx-context.jsonld
• SPDX JSON Schema: https://spdx.org/schema/3.0.1/spdx-json-schema.json
• RDF ontology: https://spdx.org/rdf/3.0.1/spdx-model.ttl
• Annotations https://spdx.org/rdf/3.0.1/spdx-json-serialize-annotations.ttl
• https://spdx.org/rdf/ontology/spdx-3-0-1 - SPDX and RDF Ontology is a 404 #1078
• Update URLs in serialization docs to 3.0.1 spdx-3-model#849

URLs are based on Tech call 2 April 2024.

Make sure these files are uploaded to proper locations, redirections are made, and accessible.

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List of potential places that may have those resources mentioned:

• bin/check-examples.sh
• docs/references.md
• docs/serializations.md
• docs/annexes/rdf-model.md -- will fix by Remove heading numbering, fix internal refs, standardized RFC links #1107
• examples/jsonld/package_sbom.json
• serialization/jsonld/annotations.ttl - Update base IRI in annotations.ttl to 3.0.1 #1096