Private content types excluded from generated GQL schema input types
### Node Version

20.18.1

### NPM/Yarn/PNPM Version

Yarn 1.22.22

### Strapi Version

5.8.0

### Operating System

Linux (Debian/Ubuntu)

### Database

MariaDB

### Javascript or Typescript

Typescript

### Reproduction URL

_No response_

### Bug Description

Content type schema attributes have a `private` option to indicate that the configured property should not be sent back to clients in API responses.  In the context of the Strapi-GraphQL plugin, this should exclude the property from the generated schema's `Type`s (returned from queries and mutations), but should _not_ exclude the property for the generated schema's `Input`s.  

### Steps to Reproduce

1. Open a Strapi project that is using the Strapi-GraphQL plugin
2. Create a new Strapi content type and add a attribute with `"private": true` in its configuration
3. Use the GraphQL playground to verify that the attribute is excluded from the schema's `Input`s and `Type`s
4. Remove the `"private": true` option from the attribute's configuration
5. Use the GraphQL playground to verify that the attribute is now included in the schema's `Input`s and `Type`s

### Expected Behavior

Marking a content type attribute as `private` should still allow clients to send the property in a `create` or `update` GQL mutation


### Code Snippets

The affected content type's `schema.json`:
```
{
  "kind": "collectionType",
  "collectionName": "contact_form_submissions",
  "info": {
    "singularName": "contact-form-submission",
    "pluralName": "contact-form-submissions",
    "displayName": "contact-form-submission",
    "description": ""
  },
  "options": {
    "draftAndPublish": true
  },
  "pluginOptions": {},
  "attributes": {
    "fullName": {
      "type": "string",
      "required": true
    },
    "company": {
      "type": "string"
    },
    "email": {
      "type": "email",
      "required": true
    },
    "phone": {
      "type": "string",
      "minLength": 7,
      "maxLength": 15,
      "required": true
    },
    "comment": {
      "type": "text"
    },
    "base64DataURL": {
      "type": "text"
    },
    "requestingDomain": {
      "type": "string"
    },
    "submissionTime": {
      "private": true,
      "required": true,
      "type": "float"
    }
  }
}
```

The generated `Input` type in `schema.graphql` for the content type:
```
input ContactFormSubmissionInput {
  base64DataURL: String
  comment: String
  company: String
  email: String
  fullName: String
  phone: String
  publishedAt: DateTime
  requestingDomain: String
}
```

### Additional information

- Under OS I marked "Linux (Debian/Ubuntu).  This is true, but I'm running ubuntu locally inside of WSL for local dev
- Under "Javascript or Typescript", I marked "Typescript", but we're using the `allowJs` option, and much of our source code is still in vanilla JS

### Confirmation Checklist

- [x] I have checked the existing [issues](https://github.com/strapi/strapi/issues) for duplicates.
- [x] I agree to follow this project's [Code of Conduct](https://github.com/strapi/strapi/blob/develop/CODE_OF_CONDUCT.md).