Update packages/durabletask-js-export-history/src/entity/export-job.ts

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: YunchuWang

packages/durabletask-js-export-history/src/entity/export-job.ts

@@ -200,13 +200,6 @@ export class ExportJob extends TaskEntity<ExportJobState> {
     this.state.lastModifiedAt = new Date();
   }
 
-  /**
-   * Deletes the export job entity by setting state to null.
-   */
-  delete(): void {
-    this.state = null as unknown as ExportJobState;
-  }
-
   /**
    * Starts the export orchestration by scheduling it from the entity context.
    * Uses a fixed instance ID to prevent concurrent orchestrators for the same job.