Update RELEASE.md

Author: pravinbhat

RELEASE.md

@@ -1,9 +1,9 @@
 # Release Notes
 
-## [5.2.1] - 2025-xx-xx
+## [5.2.1] - 2025-03-10
 - Implemented [`column.skip`](https://github.com/datastax/cassandra-data-migrator/blob/main/src/resources/cdm-detailed.properties#L97) feature
 
-## [5.2.0] - 2025-xx-xx
+## [5.2.0] - 2025-02-28
 - Upgraded to use Spark `3.5.5`.
 - Cassandra Docker image tag is now set to `cassandra:5`.