Chore: Fix typo in migrating-to-8.0.0.md

[stephenwade]

s/Three new rules/Four new rules/

[eslint-github-bot]

Hi @stephenwade!, thanks for the Pull Request

The first commit message isn't properly formatted. We ask that you update the message to match this format, as we use it to generate changelogs and automate releases.

• The commit message tag must be one of the following:

  The Tag is one of the following:

  • Fix - for a bug fix.
  • Update - either for a backwards-compatible enhancement or for a rule change that adds reported problems.
  • New - implements a new feature.
  • Breaking - for a backwards-incompatible enhancement or feature.
  • Docs - changes to documentation only.
  • Build - changes to build process only.
  • Upgrade - for a dependency upgrade.
  • Chore - for anything that isn't user-facing (for example, refactoring, adding tests, etc.).

  You can use the labels of the issue you are working on to determine the best tag.

• There should be a space following the initial tag and colon, for example 'New: Message'.

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[linux-foundation-easycla]

The committers are authorized under a signed CLA.

• ✅ Stephen Wade (7dd1c4e)

[netlify]

✔️ Deploy Preview for eslint ready!

🔨 Explore the source changes: 7dd1c4e

🔍 Inspect the deploy log: https://app.netlify.com/sites/eslint/deploys/6129569a0f1d99000803eb18

😎 Browse the preview: https://deploy-preview-866--eslint.netlify.app/docs/8.0.0/user-guide/migrating-to-8.0.0

[nzakas]

Thanks. This will only fix the guide on the live website, can you also submit a pull request for: https://github.com/eslint/eslint/edit/master/docs/user-guide/migrating-to-8.0.0.md

[snitin315]

eslint/eslint#14985