[Defect]: 1.7 XML schema omits protocol relatedCryptographicAssets #1018

Describe the defect

The CycloneDX 1.7 JSON schema defines
cryptoProperties.protocolProperties.relatedCryptographicAssets and marks the
older cryptoRefArray property as deprecated in favor of it. The 1.7 XML
schema, however, only allows repeated cryptoRef children under
protocolProperties; it does not define relatedCryptographicAssets there.

This makes the JSON and XML representations inconsistent. A 1.7 document with
one protocol-related cryptographic asset passes the JSON schema, but the
equivalent XML is rejected with:

Element '{http://cyclonedx.org/schema/bom/1.7}relatedCryptographicAssets':
This element is not expected. Expected is (... cryptoRef).

Expected behavior: the 1.7 XSD should permit the preferred
relatedCryptographicAssets representation for protocol properties, matching
the JSON schema and the corresponding certificate/material representations.

Additional context

• Current specification master checked at commit
  e02a34ae42a48239f54e04f75280b9000b29f1fb.
• The protocolProperties section in the vendored XSD used by
  cyclonedx-python-lib is byte-for-byte identical to the current
  specification section and has the same omission.
• No open or closed specification issue/PR matching
  relatedCryptographicAssets + protocolProperties was found before filing.
• This was found while reviewing
  cyclonedx-python-lib#1016,
  where the model can now round-trip the field but strict XML schema validation
  exposes the specification mismatch.

Report prepared with OpenAI Codex assistance and independently reproduced by
the submitter.