learn: is "how-to-install-nodejs" still need

[AugustinMauroy]

It's was originally written in nodejs.dev, and it's redirect to nodejs.org maybe because at the time of writing the download page wasn't near nodejs.dev (but I'm not sure).
I don't think there's any point in having this document anymore. Maybe we should just add a link to download at the bottom of the ‘introduction-to-nodejs’ page.

REF:

• https://github.com/nodejs/nodejs.org/blob/main/apps/site/pages/en/learn/getting-started/how-to-install-nodejs.md
• https://github.com/nodejs/nodejs.org/blob/main/apps/site/pages/en/learn/getting-started/introduction-to-nodejs.md