[select] Using render in Select.Icon do not remove the default icon

# Bug report

## Current behavior

When you use a custom icon for `Select.Icon` with `render`, it doesn't remove the default icon.

## Expected behavior

I should remove the default one just like when you use the icon as a children

## Reproducible example

```jsx
} // font icon
/>
```

## Base UI version

1.4.1

## Which browser are you using?

Brave

## Which OS are you using?

Mac OS