hadoop 2.7.3 文档 expunge 命令排版错误

在 Hadoop 2.7.3 版本的官方文档中 File System Shell 中的 expunge 命令描述中以下位置存在错误：

When checkpoint is created, recently deleted files in trash are moved under the checkpoint. Files in checkpoints older than fs.trash.checkpoint.interval will be permanently deleted on the next invocation of -expunge command.

红色字体标注的参数应该是 fs.trash.interval。这个排版错误已经在 2.8.0 和 3.0.0-alpha1 中修复，参见 Jira Issue：https://issues.apache.org/jira/browse/HADOOP-12675