chore: ignore chatroom and service conversation to fetch recipt

timestamps.

Realtime/Realtime/Conversation/LCIMChatRoom.cs

@@ -32,5 +32,9 @@ namespace LeanCloud.Realtime {
         public override Task Read() {
             return Task.CompletedTask;
         }
+
+        public override Task FetchReciptTimestamps() {
+            return Task.CompletedTask;
+        }
     }
 }

Realtime/Realtime/Conversation/LCIMConversation.cs

@@ -467,7 +467,7 @@ namespace LeanCloud.Realtime {
         /// Fetches receipt timestamp.
         /// </summary>
         /// <returns></returns>
-        public async Task FetchReciptTimestamps() {
+        public virtual async Task FetchReciptTimestamps() {
             await Client.ConversationController.FetchReciptTimestamp(Id);
         }
 

Realtime/Realtime/Conversation/LCIMServiceConversation.cs

@@ -17,5 +17,9 @@ namespace LeanCloud.Realtime {
         public async Task<bool> CheckSubscription() {
             return await Client.ConversationController.CheckSubscription(Id);
         }
+
+        public override Task FetchReciptTimestamps() {
+            return Task.CompletedTask;
+        }
     }
 }