Add node@18 to the build matrix for the GitLab image

What does this MR do and why?

Adds node@18 (current LTS) to the build image matrix. We are looking to update with:

gitlab#385512 (closed)

Checklist

• (If applicable) Add patches if required for upgrading Ruby version in https://gitlab.com/gitlab-org/gitlab-build-images/-/tree/master/patches/ruby.