message: Fixes CNCF footer link
  noticed on that the footer
  linking to `CNCF` projects was outdated and
  pointing to `sandbox` projects instead of the ones
  in incubation and graduated.
diff: @@ -51,7 +51,7 @@ class Footer extends React.Component {
  <a href="https://mailchi.mp/spotify/backstage-community">
  Subscribe to our newsletter
  </a>
  - <a href="https://www.cncf.io/sandbox-projects/">CNCF Incubation</a>
  + <a href="https://www.cncf.io/projects/">CNCF Incubation</a>
  </div>
  <div>
  <h5>More</h5>
  