update created_at when overwriting postgres keyframes

resources/sql/_ds_postgres.sql

@@ -54,7 +54,7 @@ UPDATE :i:repository-table
    SET data_type = CAST(:type::varchar AS :i:ds-type-fqn),
        data_encoding = CAST(:encoding::varchar AS :i:ds-encoding-fqn),
        reference = :reference,
-       created_at = CURRENT_TIMESTAMP(),
+       created_at = CURRENT_TIMESTAMP,
        "data" = :data
  WHERE document_id = :document-id AND version = :version;