made readError use backwardcompatible API

Author: chernser

client-v2/src/main/java/com/clickhouse/client/api/internal/HttpAPIClientHelper.java

@@ -74,8 +74,9 @@ public CloseableHttpClient createHttpClient(Map<String, String> chConfig, Map<St
     public Exception readError(ClassicHttpResponse httpResponse) {
         try (ByteArrayOutputStream out = new ByteArrayOutputStream(ERROR_BODY_BUFFER_SIZE)) {
             httpResponse.getEntity().writeTo(out);
+            String message = out.toString();
             int serverCode = getHeaderInt(httpResponse.getFirstHeader(ClickHouseHttpProto.HEADER_EXCEPTION_CODE), 0);
-            return new ServerException(serverCode, out.toString(StandardCharsets.UTF_8));
+            return new ServerException(serverCode, message);
         } catch (IOException e) {
             throw new ClientException("Failed to read response body", e);
         }