iOS provisional notification permission not working

Nobody has claimed this yet.

**Describe the bug**
Requesting provisional permissions returns `false` immediatly and does display a system prompt.

**To Reproduce**
1. Initialize the plugin using the following ios settings. Note that this call also returns false.

```
final DarwinInitializationSettings iosSettings =
const DarwinInitializationSettings(
requestAlertPermission: false,
requestSoundPermission: false,
requestBadgePermission: false,
requestProvisionalPermission: true,
requestCriticalPermission: false,
defaultPresentAlert: false,
defaultPresentSound: false,
defaultPresentBadge: false,
defaultPresentBanner: false,
defaultPresentList: false,
onDidReceiveLocalNotification: null,
notificationCategories: const [],
);
```

2. Request permission later on using the following API:

```
requestPermissions(
sound: false,
alert: false,
badge: false,
provisional: true,
critical: false,
);
```

3. Receive a false response and notifications cannot be scheduled.

**Expected behavior**
Provisional notifications should be granted automatically as described in the docs [here](https://developer.apple.com/documentation/usernotifications/asking_permission_to_use_notifications#3544375).

Maybe related: This [line](https://github.com/MaikuB/flutter_local_notifications/blob/2783939a3d678d9040b950f44e0e832dcd7ae5a8/flutter_local_notifications/lib/src/platform_specifics/darwin/initialization_settings.dart#L40) in the code comments mentions needing special approval from Apple to use provisional permissions. But I can't see any references to it at the linked page.

Start with flutter_local_notifications/lib/src/platform_specifics/darwin/initialization_settings.dart and trace the requestPermissions API for the provisional option on iOS. Compare the initialization and later permission-request paths with Apple's provisional notification behavior; done means both calls return the expected permission result and notifications can be scheduled without an unexpected system prompt.

Written by the indexing model from the issue text.