fix(core): Correct yarn version detection

[0420syj]

Pre-flight checklist

• I have read the Contributing Guidelines on pull requests.
• If this is a code change: I have written unit tests and/or added dogfooding pages to fully verify the new behavior.
• If this is a new API or substantial change: the PR has an accompanying issue (closes #0000) and the maintainers have approved on my working plan.

Motivation

I checked PR #8908.
However, the presence of a .yarnrc.yml file alone is not a definitive indicator of Yarn 2+ being used, as this file can be used by Yarn 1.x as well.

Check out the capture image below

Test Plan

• Check out an older docusaurus project and copy the file in place.
• Install the project with npm
• Run a npm run start
• Close and run it again
  • Confirm the notice had an appropriate npm i command
• rm -rf node_modules
• Install with yarn classic
• Run yarn start
• Close and run it again
  • Confirm the notice had an appropriate npm i command
• rm -rf node_modules
• Repeat with yarn 2

Test links

Deploy preview: https://deploy-preview-9005--docusaurus-2.netlify.app/

Related issues/PRs

#8908

[slorber]

Hi

Wonder what made you close this PR. Is the problem still relevant? Wasn't it a good solution?

cc @andrewnicols

[0420syj]

@slorber
Hi
I closed this PR for my simple mistake. I made little improvement compare to this one in #9006.

I thought I should make only 1 commit in 1 PR, so I opened new PR. The moment I noticed that I could have just squash and force push, I have already created new PR. Sorry for that happended 😅

[slorber]

I see thanks didn't notice the other PR yet 😅