The revisions endpoints provide an incorrect JSON schema

[johnbillion]

The schema provided by the REST API endpoints for revisions at wp/v2/posts/{id}/revisions and wp/v2/pages/{id}/revisions is incorrect. The schema states that content.protected and excerpt.protected properties exist for each revision, but these properties do not exist.

• ​The schema is constructed here from the parent controller for posts, which does include this property
• ​When the content data is prepared here the protected property is not included
• ​When the excerpt data is prepared here the protected property is not included

Two options:

1. Remove the content.protected and excerpt.protected properties from the schema
2. Add the content.protected and excerpt.protected properties to the response

Here is the content property from the schema. Note the protected.context property states that the property exists for all three contexts.

"content": {
    "description": "The content for the post.",
    "type": "object",
    "context": [
        "view",
        "edit"
    ],
    "properties": {
        "raw": {
            "description": "Content for the post, as it exists in the database.",
            "type": "string",
            "context": [
                "edit"
            ]
        },
        "rendered": {
            "description": "HTML content for the post, transformed for display.",
            "type": "string",
            "context": [
                "view",
                "edit"
            ],
            "readonly": true
        },
        "block_version": {
            "description": "Version of the content block format used by the post.",
            "type": "integer",
            "context": [
                "edit"
            ],
            "readonly": true
        },
        "protected": {
            "description": "Whether the content is protected with a password.",
            "type": "boolean",
            "context": [
                "view",
                "edit",
                "embed"
            ],
            "readonly": true
        }
    }
},

[johnbillion]

Update: the same applies to excerpt.protected too.

Trac ticket: https://core.trac.wordpress.org/ticket/53417

The schema provided by the REST API endpoints for revisions at wp/v2/posts/{id}/revisions and wp/v2/pages/{id}/revisions incorrectly states that content.protected and excerpt.protected properties exist. Revisions do not inherently support password protection in their response payloads, as they belong to the parent post.

This PR fixes the issue by removing the protected property from the revision schema for both the content and excerpt fields within WP_REST_Revisions_Controller::get_item_schema().

### Use of AI Tools

AI assistance: Yes
Tool(s): Github Copilot (Claude 4.6 Sonnet, Gemini 3.1 Pro)
Used for: Discussing the implementation approach and refining the PHPUnit tests for schema validation. Final code and tests were reviewed and verified locally by me.