[Bug] Fill width issue on Page Structure items with "variable level"

### Description

When swapping to the "variable level" variant of a Page Structure item, the component does not fill the expected width correctly.

### Steps to reproduce

- Add a Page Structure component to the canvas
- Swap an item to the "variable level" variant
- Observe that the item no longer fills with width of the container

Start by opening the Page Structure component in the Figma library and reproduce the issue by swapping an item to the "variable level" variant. Inspect how that variant sizes itself relative to the container. Done means the item fills the expected container width after the swap.

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