fix(assets): remove invalid Setting requirement

[ryanduguid]

Summary

• remove the nonexistent name required field from the Assets Setting response schema
• align the schema with the documented GET /Settings fields (assetNumberPrefix, assetNumberSequence, assetStartDate, and related settings)

Setting is only used by the GET /Settings response. Its example contains no name property, and the schema does not define one.

Verification

• parsed the OpenAPI YAML with PyYAML
• validated documented Settings response fields with jsonschema
• ran npx -y @redocly/cli lint xero_assets.yaml --format json and confirmed no undefined required-property warning remains for Setting

The regression validation fails on master because the schema requires nonexistent name.