Tick boxes remain highlighted with outer circle unless a page click is performed elsewhere

## Bug Description

While on the initial Site Kit setup screen, the tick boxes remain highlighted with outer circle unless a page click is performed elsewhere. This is illustrated in the screenshot below where I have selected the box once and again to de-select it but the box is still highlighted until I perform a page click somewhere else on the page.

## Steps to reproduce

1. Install the Site Kit plugin
2. Start the setup
3. On the initial page, select one of the tick boxes
## Screenshots

## Additional Context

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## Acceptance criteria

*

## Implementation Brief

* [ ]

### Test Coverage

*

## QA Brief

*

## Changelog entry

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Start at the initial Site Kit setup screen and reproduce the checkbox focus state by selecting and deselecting a tick box, then clicking elsewhere to compare the result. Trace the setup screen's checkbox component and its existing UI tests, if present; done means a deselected box no longer remains surrounded by the highlighted outer circle before another page click.

Written by the indexing model from the issue text.