fix: os/gcron: unit testing case of package gcron occasionally failed

[wanghaolonggit]

[gqcn]

@wanghaolonggit 你好，感谢参与开源共建。这里针对定时任务的修复不应当通过额外的锁机制来保证执行完毕，应该根据日志的打印时间来判断为什么单测不满足断言条件，根据排查的结果，可能需要对定时任务或者单测逻辑进行改进。

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@wanghaolonggit Hello, thank you for participating in open source co-construction. The repair of scheduled tasks here should not use additional lock mechanisms to ensure completion of execution. The printing time of the log should be used to determine why the single test does not meet the assertion conditions. Based on the results of the investigation, the scheduled tasks or single test logic may need to be improved. .