Set-Cookie is not updated after changing `cookie` config even when `rolling` is set to true

## Environment information

**Version**: 1.18.2

**Platform**: All

**Node.js version**: v22.17.1

**Any other relevant information**: -

## What steps will reproduce the bug?

Config I'm using:

```js
app.use(expressSession({
secret: '...',
name: "sessionId",
store: new (require('connect-pg-simple')(expressSession))(),
cookie: {
httpOnly: true,
secure: true,
domain: "example.com",
sameSite: "none",
maxAge: 7 * 24 * 60 * 60 * 1000 // 7 days
},
proxy: true,
resave: false,
saveUninitialized: false,
rolling: true,
}));
```

If I change e.g. `sameSite` to "strict", or change `maxAge`, this only applies to brand new sessions. I would expect that with `rolling: true`, these changes would apply to existing cookies too when the user next time uses the app.