[bug] Using plugin-dialog and plugin-fs to write file on iOS is ineffective.

Replicate the code：https://github.com/shell360/tauri-issue
The replication steps：
1. `git clone https://github.com/shell360/tauri-issue.git`
2. `cd tauri-issue && pnpm install`
3. run `pnpm tauri ios dev`，And select the iOS simulator.
4. click `save file` button
5. When checking the file in iOS file management, it was found that the content was not successfully written.

```tsx
import { useCallback, useState } from 'react'
import { save, open } from '@tauri-apps/plugin-dialog'
import { writeFile, readFile } from '@tauri-apps/plugin-fs'

function App() {
const onSave = useCallback(async () => {
const path = await save()
if (!path) {
return
}

let encoder = new TextEncoder()
let data = encoder.encode('Hello World')
await writeFile(path, data) // The content was not successfully written.
}, [])

const onOpen = useCallback(async () => {
const path = await open()
if (!path) {
return
}

let content = await readFile(path)
console.log(content)
}, [])

return (

save file
open file

)
}

export default App

```