docs: Update fixedColumns.tsx code (#1033)

Make code work

Author: zhouzhongyuan

docs/examples/fixedColumns.tsx

@@ -1,7 +1,7 @@
 import React from 'react';
 import Table from 'rc-table';
-import '../../assets/index.less';
-import { ColumnType } from '@/interface';
+import { ColumnType } from 'rc-table/lib/interface';
+import './assets/index.less';
 
 interface RecordType {
   a: string;