LFX Mentorship: Kselftest Patch Submission - Message Clarity Improvement in futex_requeue

Hi maintainers,

As part of the Kselftest task for the LFX Mentorship Program, I have reviewed the futex selftest and made minor improvements to the message clarity in `futex_requeue.c`.

Attached is the patch with the changes. I’ve also uploaded it to the mentorship platform as instructed.

Please let me know if any changes are needed.

Thanks, Shivam Sharma 10sharmashivam@gmail.com