chore: deprecate exitLiveActivity API and remove demo UI

Author: fadi-george

examples/demo/lib/widgets/sections/live_activities_section.dart

@@ -82,18 +82,6 @@ class _LiveActivitiesSectionState extends State<LiveActivitiesSection> {
                 : () => vm.updateLiveActivity(),
           ),
           AppSpacing.gapBox,
-          SizedBox(
-            width: double.infinity,
-            child: OutlinedButton(
-              onPressed: activityEmpty ? null : () => vm.exitLiveActivity(),
-              style: OutlinedButton.styleFrom(
-                foregroundColor: AppColors.osPrimary,
-                side: const BorderSide(color: AppColors.osPrimary),
-              ),
-              child: const Text('STOP UPDATING LIVE ACTIVITY'),
-            ),
-          ),
-          AppSpacing.gapBox,
           SizedBox(
             width: double.infinity,
             child: OutlinedButton(

lib/src/liveactivities.dart

@@ -5,7 +5,7 @@ class OneSignalLiveActivities {
   // private channels used to bridge to ObjC/Java
   MethodChannel _channel = const MethodChannel('OneSignal#liveactivities');
 
-  /// Indicate this device has exited a live activity, identified within OneSignal by the [activityId]. The
+  /// Indicate this device has entered a live activity, identified within OneSignal by the [activityId]. The
   /// [token] is the ActivityKit's update token that will be used to update the live activity.
   ///
   /// Only applies to iOS.
@@ -19,6 +19,7 @@ class OneSignalLiveActivities {
   /// Indicate this device has exited a live activity, identified within OneSignal by the [activityId].
   ///
   /// Only applies to iOS.
+  @Deprecated('This API is no longer supported and will be removed in a future release.')
   Future<void> exitLiveActivity(String activityId) async {
     if (defaultTargetPlatform == TargetPlatform.iOS) {
       return await _channel.invokeMethod(