Incorrect proguard configuration for `Mapbox_TripNotificationModuleConfiguration`

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**Mapbox Navigation SDK version:** 1.6.1

### Steps to trigger behavior

1. Create a custom trip notification as explained [here](https://docs.mapbox.com/android/navigation/guides/modularization/#replacing-a-module)
2. Enable code shrinking and obfuscation by adding `minifyEnabled true` to the `build.gradle` file
3. Build the app

### Expected behavior
The generated `Mapbox_TripNotificationModuleConfiguration` class and its nested interface `ModuleProvider` are annotated with `@Keep` rules to prevent the code shrinking tool from removing it from the app,

### Actual behavior
Only the `Mapbox_TripNotificationModuleConfiguration` has the `@Keep` annotation and the `ModuleProvider` doesn't. This forces library user to manually add a keep rule to their `proguard-rules.pro` file (e.x. `-keep interface com.mapbox.module.Mapbox_TripNotificationModuleConfiguration$ModuleProvider { *; }
`)

Here's how the generated class looks like now (the `ModuleProvider` is missing the `@Keep` annotation)
``` kotlin
/**
* Configuration provider for TripNotification module.
*/
@Keep
object Mapbox_TripNotificationModuleConfiguration {
@JvmStatic
val enableConfiguration: Boolean = true

/**
* Set this dependency provider before initializing any components of the modularized library.
*
* When you're not using the library anymore, you should pass `null` to clean up the provider
* reference and prevent memory leaks.
*/
@JvmStatic
var moduleProvider: ModuleProvider? = null

interface ModuleProvider {
fun createTripNotification(): TripNotification
}
}
```

Locate the source or generation entry point for Mapbox_TripNotificationModuleConfiguration, then compare its annotations with the nested ModuleProvider interface. Use the minifyEnabled true scenario from the issue and the proguard-rules.pro workaround to verify that the generated interface is retained without a manual keep rule.

Written by the indexing model from the issue text.