You have to click on latest in the left top or use this link (which is currently loading very slooooow): Google Assistant | openHAB
Wait. Stop. The update has not been merged yet. See [Automated] Fetch openhab-google-assistant docs by github-actions[bot] · Pull Request #2301 · openhab/openhab-docs · GitHub.
So you have to look here for now: openhab-google-assistant/docs/USAGE.md at main · openhab/openhab-google-assistant · GitHub