Don't log an error for cancellation

Author: davidwengier

src/Razor/src/Microsoft.CodeAnalysis.Razor.CohostingShared/HtmlDocumentServices/HtmlDocumentSynchronizer.cs

@@ -174,6 +174,11 @@ private async Task<SynchronizationResult> PublishHtmlDocumentAsync(TextDocument
 
             return result;
         }
+        catch (OperationCanceledException)
+        {
+            _logger.LogDebug($"Not publishing Html text for {document.FilePath} as the request was cancelled.");
+            return default;
+        }
         catch (Exception ex)
         {
             _logger.LogError(ex, $"Error publishing Html text for {document.FilePath}. Html document contents will be stale");