fix: checkstyle

Author: suhwan-cheon

flink-cdc-connect/flink-cdc-source-connectors/flink-connector-mysql-cdc/src/test/java/org/apache/flink/cdc/connectors/mysql/source/MySqlSourceITCase.java

@@ -1535,9 +1535,9 @@ void testUnsignedBigintPrimaryKeyChunking() throws Exception {
 
     private String stringifyUnsignedPkRow(RowData row) {
         DecimalData decimal = row.getDecimal(0, 20, 0);
-        String order_id = decimal.toBigDecimal().toPlainString();
+        String orderId = decimal.toBigDecimal().toPlainString();
         String desc = row.getString(1).toString();
-        return "+I[" + order_id + ", " + desc + "]";
+        return "+I[" + orderId + ", " + desc + "]";
     }
 
     /**