(DOCSP-21040) Update DataLake's relnotes from June 2021 (#237)

Author: JuliaMongo

source/includes/changelog/data-lake-2021.rst

@@ -130,7 +130,7 @@
 
 - Improves stability and performance.
 - Supports public S3 data stores with the ``public`` configuration flag.
-- Supports Zstandard compression.
+- Supports Zstandard compression when federating queries to |service| clusters.
 - Adds ``db`` field to ``dbStats`` result.
 
 .. _data-lake-v20210511: