Replace go-migrate with morph (#19116)

db/migrations/postgres/000053_create_retention_policies.down.sql

@@ -0,0 +1,12 @@
+DROP INDEX IF EXISTS IDX_RetentionPolicies_DisplayName;
+CREATE INDEX IF NOT EXISTS IDX_RetentionPolicies_DisplayName_Id ON retentionpolicies (displayname, id);
+
+ALTER TABLE retentionpolicieschannels DROP CONSTRAINT IF EXISTS fk_retentionpolicieschannels_retentionpolicies;
+ALTER TABLE retentionpoliciesteams DROP CONSTRAINT IF EXISTS fk_retentionpoliciesteams_retentionpolicies;
+
+DROP INDEX IF EXISTS IDX_RetentionPoliciesChannels_PolicyId;
+DROP INDEX IF EXISTS IDX_RetentionPoliciesTeams_PolicyId;
+
+DROP TABLE IF EXISTS retentionpolicieschannels;
+DROP TABLE IF EXISTS retentionpoliciesteams;
+DROP TABLE IF EXISTS retentionpolicies;