Clarification needed: Properties marked both required and readOnly in relationships.json

## Description

In the [relationships.json specification](https://github.com/Azure/azure-rest-api-specs/blob/main/specification/relationships/resource-manager/Microsoft.Relationships/preview/2023-09-01-preview/relationships.json#L687), the `ServiceGroupMemberRelationshipProperties` schema defines three properties (`metadata`, `sourceId`, and `originalInformation`) that are marked as both `required` and `readOnly`.

Start at specification/relationships/resource-manager/Microsoft.Relationships/preview/2023-09-01-preview/relationships.json around line 687 and inspect the ServiceGroupMemberRelationshipProperties schema and its metadata, sourceId, and originalInformation properties. Compare the required and readOnly declarations with the surrounding specification conventions; the issue is done when the intended schema behavior is clarified and the specification is updated accordingly.

Written by the indexing model from the issue text.