docs: update Node.js requirements for Corepack

[TheConstructor]

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According to https://nodejs.org/dist/latest/docs/api/corepack.html, https://nodejs.org/en/blog/release/v14.19.0/ and https://nodejs.org/en/blog/release/v16.9.0/ corepack did not start shipping in 16.10 but 16.9 and is also included in v14 starting with 14.19. Trying to follow the instructions, when corepack is already provided, leads to errors with code EEXIST

Checklist

• [x] I have read the Contributing Guide.

• [ ] I have set the packages that need to be released for my changes to be effective.

• [x] I will check that all automated PR checks pass before the PR gets reviewed.

[TheConstructor]

Iirc the 16.9 Corepack had a bug that prevented yarn init -2 from working, so it's only viable starting from 16.10

@arcanis Ok, but would installing corepack work in 16.9?

[TheConstructor]

@arcanis I finally found some minutes to prepare a Docker-image and use https://containers.dev/ to run some tests. I didn't manage to get corepack to correctly run yarn with 16.9, when I issued corepack enable before running npm i -g corepack, so you are definitely right, that corepack enable shouldn't be suggested. I added a warning, so hopefully few people encounter my problems.

[merceyz]

Closing since the live documentation no longer mentions the Node.js version ranges.