Update token_troubleshooting.md with notes about PrAT/GrAT

What does this MR do and why?

Based on Group access token with an updated expires_at d... (#482845 - closed) we learned that users could potentially be using the token troubleshooting script, created for tokens that were given an automatic expiration to also manage PrATs/GrAT expiry for tokens that they had created with an expiration or had been rotated. As these tokens have expiration thats actually tied to their membership of a project or group resource, these can't be extended. We should also not modify the membership expiration directly, as an upcoming feature reliese on the presence of that membership to list expired to tokens and eventually clean them up from DB/UI

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.