Before, it just said `SuperJSON.deserialize(props.pageProps.dehydratedState)`. This didn't work since it doesn't account for babel-plugin-superjson-next to pick different superjson keys than SuperJSON itself :( SuperJSON expects a `json` and a `meta` key, while babel-plugin-superjson-next puts the meta right into the props and calls it `_superjson`. This commit fixes that behaviour, and makes sure that dehydratedState works both for SSR and for client-side.