Fix broken link to community handbook

[larsks]

The main page was pointing to /hitchhikers-guide instead of /community-handbook

Closes operate-first/support#517

[netlify[bot]]

✔️ Deploy Preview for relaxed-goldstine-ebb96e ready!

🔨 Explore the source changes: 9cbb4104a08dee3d4568dcee8e325652a292b16e

🔍 Inspect the deploy log: https://app.netlify.com/sites/relaxed-goldstine-ebb96e/deploys/61f996dacb10aa000891e4d1

😎 Browse the preview: https://deploy-preview-355--relaxed-goldstine-ebb96e.netlify.app

[HumairAK]

/lgtm /approve