Fix grammar error in walkthrough lesson 4

[vladbndko]

Remove double 'to add' from Lesson 4 in the walkthrough

[changeset-bot]

⚠️ No Changeset found

Latest commit: 4656742

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[vercel]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Updated
keystone-next-docs	✅ Ready (Inspect)	Visit Preview	May 30, 2022 at 8:25PM (UTC)

[codesandbox-ci]

This pull request is automatically built and testable in CodeSandbox.

To see build info of the built libraries, click here or the icon next to each commit SHA.

[dcousens]

Thanks @vladbndko