[ci] Temporarily always build from source for codesandbox

We need a GitHub token to download artifacts from GitHub so
unfortunately codesandboxci will need to revert to the slower process
of building from source for now until it's possible to pass secrets to
codesandboxci.

ghstack-source-id: edab9790847f7f9539d302f10b59b74f6187fbdc
Pull Request resolved: https://github.com/facebook/react/pull/30511