Un-subscribe from proactive events request the CustomProactiveSubscriptionChangedRequestHandler.java

ProactiveSubscriptionChanged.json

{
    "request": {
        "timestamp": "2019-06-10T12:50:52Z",
        "requestId": "0f5ed9e2-267e-4231-9c15-6b8f4b74e957",
        "type": "AlexaSkillEvent.ProactiveSubscriptionChanged"
    },
    "version": "1.0",
    "context": {
        "System": {
            "apiEndpoint": "https://api.amazonalexa.com",
            "user": {
                "userId": "amzn1.ask.account.AFJ..."
            },
            "application": {
                "applicationId": "amzn1.ask.skill.e2a..."
            }
        }
    }
}