deps: upgrade Dockerfile to Node.js 20 LTS

[bajtos]

Interestingly enough, this seems to fix the network errors we observed before 🤷🏻‍♂️

Example of such errors:

npm ERR! code ECONNRESET
npm ERR! errno ECONNRESET
npm ERR! network request to https://registry.npmjs.org/is-network-error/-/is-network-error-1.0.0.tgz failed, reason: socket hang up
npm ERR! network This is a problem related to network connectivity.
npm ERR! network In most cases you are behind a proxy or have bad network settings.

[bajtos]

If we encounter this problem in the future, another possible fix is to upgrade npm to the latest version as part of our Dockerfile script. Quoting from nodejs/docker-node#1668 (comment):

RUN npm cache clean --force && \
    npm install -g npm@latest && \
    npm install

[bajtos]

https://github.com/filecoin-station/core/releases/tag/v16.1.1