fix(select-modal): hide focus option's border for ionic theme (#30660)

Issue number: resolves internal

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## What is the current behavior?
When opening a ion-select with a modal interface, the first option is
focused and, as such, has a border.
This happens because an ion-item is being rendered, which has a specific
styling for focused stated.

## What is the new behavior?
When inside a `ion-select-modal`, we don't want this specific `ion-item`
styling.

## Does this introduce a breaking change?
- [ ] Yes
- [x] No