Clean up findFiberByHostInstance from DevTools Hook (#31711)

The need for this was removed in
https://github.com/facebook/react/pull/30831

Since the new DevTools version has been released for a while and we
expect people to more or less auto-update. Future versions of React
don't need this.

Once we remove the remaining uses of `getInstanceFromNode` e.g. in the
deprecated internal `findDOMNode`/`findNodeHandle` and the event system,
we can completely remove the tagging of DOM nodes.