bugfix: remove nodejs engines requirement until further discussion with other contributors

[jameslinjl]

• I had initially added the engines requirement when thinking about how to lock down the Node runtime for code-gen
• However, I failed to realize that the engines requirement would be applied for usages of the published package as well
• We should probably establish a reasonable engines minimum requirement still (open to suggestions), but I already published this as a patch fix in order to unbreak the published npm package
• Using engines to lock down the code-gen Node runtime is also unnecessary now, since the base docker image will take care of that for us

[jameslinjl]

@gauthier-th @derhuerst I think it makes sense to merge this first to reflect what has been published to NPM, and then we should circle back and discuss what reasonable engines boundaries might be

[jameslinjl]

@isabelle-dr if you're able to merge this PR, that would be great! it's a fix for a publishing issue I ran into yesterday