CLI: Use npm install when setting up Gutenberg

[jhnstn]

Gutenberg has a package-lock linter to make sure the local package versions match what's in the package lock.
Running npm ci won't update the lock file but npm i will

This changes the npm command to use install

Testing:

• Try preparing Gutenberg for a release
• Verify that the root package-lock.json file is updated.

[derekblank]

LGTM. 🚀