Investigate `assets/js/components/FeatureTours.js` to potentially refactor/move `useEffect` code

## Feature Description

Raised [here](https://github.com/google/site-kit-wp/pull/11271#discussion_r2289035453), we should investigate logic within `useEffect` hook

> why not just add this as an effect into the main dashboard? Why do we have a ResizeObserver which simply emits resize events? Is this even still needed? (Maybe newer versions of Joyride have addressed this?) Why is this only concerned with the main dashboard when this component is rendered as part of Root?

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## Acceptance criteria

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## Implementation Brief

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### Test Coverage

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## QA Brief

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## Changelog entry

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Start by reading assets/js/components/FeatureTours.js and the discussion in pull request #11271. Trace the useEffect, ResizeObserver, and Joyride-related behavior when FeatureTours is rendered from Root and on the main dashboard. Done means deciding whether the logic is still needed and documenting or implementing its appropriate location, with relevant tests updated if identified.

Written by the indexing model from the issue text.