schema.sql: Fix syntax error

schema.sql

@@ -355,7 +355,7 @@ CREATE TABLE user_webhook_subscription (
 	created timestamp without time zone NOT NULL,
 	url character varying(2048) NOT NULL,
 	events character varying NOT NULL,
-	user_id integer REFERENCES "user"(id), ON DELETE CASCADE
+	user_id integer REFERENCES "user"(id) ON DELETE CASCADE,
 	token_id integer REFERENCES oauthtoken(id) ON DELETE CASCADE
 );