RadioButton.Item has duplicate tabstop

### Current behaviour
RadioButton.Item contains two elements with a tabIndex of 0, so it takes 2 tabs to go past it.

### Expected behaviour
There should be only one tabbable element, since they do the same thing

### How to reproduce?
Issue is visible in the example snack () under the "Radio Button Item" page, at least on the Web platform. Click an item, and then press Tab a few times to observe the behaviour

### Preview

### What have you tried so far?
nothing

### Your Environment

| software | version
| --------------------- | -------
| ios | n/a
| android | n/a
| react-native | 0.80.1
| react-native-paper | 5.14.5
| node | 22.13.1
| npm or yarn | npm 10.9.2
| expo sdk | n/a

从 RadioButton.Item 的实现开始，在 Web 平台上链接的 Expo Snack 中复现该问题。验证 RadioButton.Item 只暴露一个可通过 Tab 访问的元素，并且按下 Tab 后会越过该元素一次。

由索引模型根据 Issue 内容生成。