revert unintended change

packages/coreutils/src/pageconfig.ts

@@ -160,6 +160,17 @@ export namespace PageConfig {
     return getOption('token') || getBodyData('jupyterApiToken');
   }
 
+  /**
+   * Get the Notebook version info [major, minor, patch].
+   */
+  export function getNotebookVersion(): [number, number, number] {
+    const notebookVersion = getOption('notebookVersion');
+    if (notebookVersion === '') {
+      return [0, 0, 0];
+    }
+    return JSON.parse(notebookVersion);
+  }
+
   /**
    * Private page config data for the Jupyter application.
    */