make _event_type varchar(64) instead of enum

Signed-off-by: Pawel Leszczynski <leszczynski.pawel@gmail.com>

Author: pawel-big-lebowski

api/src/main/resources/marquez/db/migration/V66.2__alter_lineage_events_add_event_type.sql

@@ -1,4 +1,2 @@
-CREATE TYPE EVENT_TYPE AS ENUM ('RUN_EVENT', 'DATASET_EVENT', 'JOB_EVENT');
-
-ALTER TABLE lineage_events ADD COLUMN _event_type EVENT_TYPE;
+ALTER TABLE lineage_events ADD COLUMN _event_type VARCHAR(64);
 ALTER TABLE lineage_events ALTER COLUMN _event_type SET DEFAULT 'RUN_EVENT';