message: remove logging error message when delta manager closed due to error
  ## Description
  we will no longer include error message in the disconnect reason. This
  way in kusto, we can aggregate "closing deltamanager" , while now they
  are all different because the error message is different.
diff: @@ -355,10 +355,7 @@ export class ConnectionManager implements IConnectionManager {
  this._outbound.clear();
  - const disconnectReason =
  - error !== undefined
  - ? `Closing DeltaManager (${error.message})`
  - : "Closing DeltaManager";
  + const disconnectReason = "Closing DeltaManager";
  // This raises "disconnect" event if we have active connection.
  this.disconnectFromDeltaStream(disconnectReason);
  