doc: services: debugging: Remove unwanted reference link

[afesheir]

Remove unwanted reference link to the section (Usage) in ARM Coresight Trace Deformatter that shows up in the main Debugging documentation page, by lowering the level of (Usage) heading from ##### to *****

The commit also has a typo fix.

[github-actions]

Hello @afesheir, and thank you very much for your first pull request to the Zephyr project!
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[kartben]

@afesheir Thanks much for taking the time to both open an issue and a pull request to get this fixed. Much appreciated!

[github-actions]

Hi @afesheir!
Congratulations on getting your very first Zephyr pull request merged 🎉🥳. This is a fantastic achievement, and we're thrilled to have you as part of our community!

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Thank you for your valuable input, and we look forward to seeing more of your contributions in the future! 🪁