fix test

Author: KirillKurdyukov

src/Ydb.Sdk/src/Services/Topic/Writer/Writer.cs

@@ -336,7 +336,7 @@ public async ValueTask DisposeAsync()
         await _sendInFlightMessagesSemaphoreSlim.WaitAsync();
         try
         {
-            _disposeCts.Dispose();
+            _disposeCts.Cancel();
         }
         finally
         {

src/Ydb.Sdk/tests/Topic/WriterUnitTests.cs

@@ -719,7 +719,7 @@ public async Task WriteAsync_WhenWriterIsDisposed_ThrowWriterException()
             { ProducerId = "producerId" }.Build();
         await writer.DisposeAsync();
 
-        Assert.Equal("Writer[TopicPath: /topic-15, ProducerId: producerId, Codec: Raw] is disposed",
+        Assert.Equal("Writer[TopicPath: /topic-14, ProducerId: producerId, Codec: Raw] is disposed",
             (await Assert.ThrowsAsync<WriterException>(() => writer.WriteAsync("abacaba"))).Message);
     }