We don't actually use this anywhere, so let's remove it.

https://github.com/facebook/react/blob/f1d00156df5453bc62bd5668fefdcac4ca67e90e/src/renderers/shared/fiber/ReactFiberScheduler.js#L1504-L1512
type: T,
    props: P,
    rootContainerInstance: C,
    internalInstanceHandle: OpaqueHandle,
  ) => null | PL,
  hydrateTextInstance?: (
    textInstance: TI,
    text: string,
    internalInstanceHandle: OpaqueHandle,
  ) => boolean,
  didNotHydrateInstance?: (parentInstance: I | C, instance: I | TI) => void,
  didNotFindHydratableInstance?: (
    parentInstance: I | C,
    type: T,
    props: P,
  ) => void,
  didNotFindHydratableTextInstance?: (
    parentInstance: I | C,
    text: string,
  ) => void,
  useSyncScheduling?: boolean,
};
export type Reconciler<C, I, TI> = {
  createContainer(containerInfo: C): OpaqueRoot,
  updateContainer(
    element: ReactNodeList,
    container: OpaqueRoot,
    parentComponent: ?React$Component<any, any>,
    callback: ?Function,
  ): void,