Make work item edited text gray secondary

What does this MR do and why?

Aligns edited text in work items with legacy issues. Currently this is aligned when viewing a task in the contextual view, but not the full page view, as it's referencing a class in a page bundle that is not loaded for work items (in contextual view, page bundle is loaded for the parent issue and available for task modal).

This MR moves the styles applied by edited-text into utility classes to avoid reliance on page bundles. This does not remove edited text as it remains used in a few other places.

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