Drop default Null for renew_time in sql

docs/schema-upgrade-1.32-1.33.sql

@@ -2,6 +2,6 @@
 -- from version 1.32 to 1.33
 
 BEGIN;
-    ALTER TABLE sessions ADD COLUMN renew_time TIMESTAMPTZ DEFAULT NULL;
+    ALTER TABLE sessions ADD COLUMN renew_time TIMESTAMPTZ;
 COMMIT;
 

docs/schema.sql

@@ -120,7 +120,7 @@ CREATE TABLE sessions (
 	update_time TIMESTAMPTZ NOT NULL DEFAULT NOW(),
 	exclusive BOOLEAN CHECK (exclusive),
 	closed BOOLEAN NOT NULL DEFAULT FALSE,
-	renew_time TIMESTAMPTZ DEFAULT NULL,
+	renew_time TIMESTAMPTZ,
 	CONSTRAINT no_exclusive_subsessions CHECK (
 		master IS NULL OR "exclusive" IS NULL),
 	CONSTRAINT no_closed_exclusive CHECK (