This reverts commit b2ae9ddb3b.
While the feature flag is fully rolled out, these tests are also testing
behavior set with an unstable flag on root, which for now we want to
preserve.
Not sure if there's a better way then adding a dynamic feature flag to
the www build?
DiffTrain build for commit https://github.com/facebook/react/commit/da94e8b24a3f31a3e805f9bf6bba73055aad9d41.