out_s3: Align headers

Signed-off-by: Hiroshi Hatake <[email protected]>

Author: cosmo0920

pipeline/outputs/s3.md

@@ -721,9 +721,7 @@ cmake --build .
 For other Linux distributions, refer [the document for installation instructions of Apache Parquet](https://arrow.apache.org/install/).
 Apache Parquet GLib is a part of Apache Arrow project.
 
-### Testing Parquet compression
-
-## Testing (Parquet)
+### Testing Parquet support
 
 Example configuration: