Fix outdated example path in README.
Fix outdated example path in README.

PiperOrigin-RevId: 399626816
Change-Id: I725c29e3073c9a1a17485b5bed3d8863e1b7d83e
GitOrigin-RevId: 1411dbfd588caca787b9cca7d053002154d5002a

deepmind/xmanager,deepmind/xmanager