iOS app open/close transition shows shadow on SegmentedButtons

### Current behaviour
I am rendering a Segmented Button (basic, vanilla implementation)
When I open or close the iOS app, I see a gradient within one of the segments.

### Expected behaviour
No gradient.

### How to reproduce?
Use iOS
Add a segmented button to your view.
Close or open the iOS app to show the gradient.

### Preview
Implementation:
``

Screenshot:

### What have you tried so far?
Explicitly setting a background color with
`style={[styles.group, { backgroundColor: theme.colors.background }]}`

### Your Environment

| software | version
| --------------------- | -------
| ios | 16.0
| react-native | 0.76.3
| react-native-paper | ^5.12.5

从 SegmentedButtons 的实现开始，使用 issue 中的 vanilla segmented-button 示例在 iOS 16.0 上复现该过渡效果。当打开或关闭应用时，segment 内不再显示渐变或阴影，即表示完成。

由索引模型根据 Issue 内容生成。