Fix test case: PlainPermissionManagerTest#multiFilePathTest

[mxsm]

https://github.com/apache/rocketmq/runs/8173679384?check_suite_focus=true

[github-actions]

This issue is stale because it has been open for 365 days with no activity. It will be closed in 3 days if no further activity occurs.

[github-actions]

This issue was closed because it has been inactive for 3 days since being marked as stale.