Unable to Remove Persistent Shadow from Modal Component in React Native Paper

### Current behaviour
I'm experiencing an issue with the Modal component in React Native Paper in iOS where I am unable to remove the shadow from the modal view. Despite trying various approaches to eliminate the shadow, it remains persistent. Where it's working fine on the android device without any shadow.

### Expected behaviour
The shadow around the Modal component should be removed based on the provided styles and theme configurations.

### Preview

### What have you tried so far?
Elevation to 0
Backdrop to white(To make the background colour of the modal white instead of opaque)

### Your Environment

| software | version
| --------------------- | -------
| ios | iOS 17.2

从 React Native Paper Modal 组件开始，使用已报告的 elevation 和 backdrop 设置，在 iOS 17.2 上复现 iOS 的行为。将其与正常工作的 Android 行为进行比较，并验证是否可以通过其样式和主题配置移除 modal 阴影。

由索引模型根据 Issue 内容生成。