Permission to edit issue metadata

What does this MR do and why?

Describe in detail what your merge request does and why.

The documentation indicates that guest users are able to create issues and add labels. There is a footnote that indicates: Guest users can only set metadata (for example, labels, assignees, or milestones) when creating an issue. They cannot change the metadata on existing issues.

This is an important information for customers when evaluating the attribution of the guest role but the footnote information is easy to miss.

This MR proposes to add a row in the table that shows the action of editing issue metadata (labels, assignees, milestones,...) as not part of the guest role.

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MR acceptance checklist

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