Don't manually remove the push subscription

* When the SDK hydrates users, it will trigger the subscription model store's `replaceAll` method. This will remove the current push subscription model and immediately add a new push subscription model. The Subscription Manager was removing the current push subscription and then adding a new push subscription that it manages. When the new one is added, the old one is removed and any observers are transferred over.
* However, because the old one was already removed by the time the new one is added, observers are lost. The [onModelAdded] already triggers an add and remove, so we should not remove in the [onModelRemoved] event.
* These 2 events are always together. There is no current usage where only [onModelRemoved] is called for a push subscription model. Even on 404s, push subscription models are not removed.

Author: nan-li

OneSignalSDK/onesignal/core/src/main/java/com/onesignal/user/internal/subscriptions/impl/SubscriptionManager.kt

@@ -190,6 +190,14 @@ internal class SubscriptionManager(
         model: SubscriptionModel,
         tag: String,
     ) {
+        // Do not remove the push subscription: we need to keep the existing push subscription and its observers
+        // This push subscription will immediately be replaced by the new one in the [onModelAdded] event
+        // The [onModelRemoved] event for a push subscription model should always be followed by a [onModelAdded]
+        // event with a new push subscription model. On 404s, no push subscription models are removed.
+        if (model.type == SubscriptionType.PUSH) {
+            return
+        }
+
         val subscription = subscriptions.collection.firstOrNull { it.id == model.id }
 
         if (subscription != null) {