upgrade to node 20

[lodewiges]

all builds are failing because our node version is to old for renovate

it needs to be above 18.17, reason: nodejs/corepack#359 (review)

however, the dockerfile depends on 18.14, https://github.com/danlynn/ember-cli/blob/4.11.0/Dockerfile

to solve this, we could upgrade to the node 20 and ember 4.12 dockerfile, https://github.com/danlynn/ember-cli/blob/4.12.1-node_20.2/Dockerfile

It would be best practice to upgrade because node 18 will be end off life in a couple months
https://endoflife.date/nodejs

upgrade blog: https://www.upgradejs.com/blog/why-and-how-to-upgrade-to-nodejs-from-v18-to-v20m-v18.html