SyncWriter.flush() now throw Exception when previous task was failed

Author: ekuvardin

topic/src/main/java/tech/ydb/topic/write/impl/WriterImpl.java

@@ -276,9 +276,7 @@ protected CompletableFuture<Void> flushImpl() {
         incomingQueueLock.lock();
 
         try {
-            return this.lastAcceptedMessageFuture.isDone()
-                    ? CompletableFuture.completedFuture(null)
-                    : this.lastAcceptedMessageFuture.thenApply(v -> null);
+            return this.lastAcceptedMessageFuture.thenApply(v -> null);
         } finally {
             incomingQueueLock.unlock();
         }