refactor: remove deprecated getDocumentId method from Editor class

- Eliminated the getDocumentId method to streamline the Editor class, as it is no longer needed following recent changes to document identifier handling.
- This refactor contributes to cleaner code and improved maintainability.

Author: caio-pizzol

packages/super-editor/src/core/Editor.js

@@ -1481,14 +1481,6 @@ export class Editor extends EventEmitter {
     return html;
   }
 
-  /**
-   * Get the document ID from the converter
-   * @returns {string|null} The unique SuperDoc ID for this document
-   */
-  getDocumentId() {
-    return this.converter?.getSuperdocId() || null;
-  }
-
   /**
    * Get the document version from the converter
    * @returns {string|null} The SuperDoc version stored in the document