Update known_issues.mdx rework data migration

Author: djw-m

product_docs/docs/postgres_distributed_for_kubernetes/1/known_issues.mdx

@@ -11,7 +11,8 @@ This version of EDB Postgres Distributed for Kubernetes **doesn't support** majo
 
 ## Data migration
 
-This version of EDB Postgres Distributed for Kubernetes **doesn't support** migrating from existing Postgres databases.
+This version of EDB Postgres Distributed for Kubernetes does not support declarative import of data from other Postgres database. 
+To migrate schemas and data, you can use `pg_dump ...` on the source database and pipe the command's output to your target database with `psql -c`.
 
 ## Connectivity with PgBouncer