request to update nodejs20-debian12 from node v20.17 to v20.18

Node v20.18.0 has an important [fix](https://github.com/nodejs/undici/pull/3445) for a memory leak which started in v20.16.0

```
$ docker run gcr.io/distroless/nodejs20-debian12 --version
v20.17.0
```

Can we get an updated version of this image published with https://nodejs.org/en/blog/release/v20.18.0