fix(files): remove invalid FileObject requirements

[ryanduguid]

Draft hold — domain decision required. Do not merge this change until the Files API owner confirms whether FileObject.Id and FileObject.Name are required response fields and whether the shared response/update schema should be split. Local schema validation cannot establish that contract.

Proposed change

• remove four undefined, lower-case required fields from the Files FileObject schema
• allow the documented partial PUT /Files/{FileId} request body (for example, { "FolderId": "..." })

FileObject is shared by file responses and the partial-update request body. Replacing the fields with Name/Id would still make valid partial updates invalid. Removing the list is mechanically consistent with the partial-update example, but may weaken the response contract; splitting request and response schemas may be the correct domain-owned solution.

Limited verification

• parsed the OpenAPI YAML with PyYAML
• validated the documented FolderId-only PUT example against the proposed FileObject with jsonschema
• npx -y @redocly/cli lint xero_files.yaml --format stylish: removes the four FileObject no-required-schema-properties-undefined warnings; the file retains unrelated baseline lint findings

These checks establish schema mechanics only. They are not authoritative evidence for Files API field requiredness.