How to clear Once in Mathematica 11.0?

In the help file it says:

Use Unset[Once[expr]] to clear a remembered value

But how do I clear it for all past expressions?

Would Clear[Once] work?

DreamProxies - Cheapest USA Elite Private Proxies 100 Private Proxies 200 Private Proxies 400 Private Proxies 1000 Private Proxies 2000 Private Proxies ExtraProxies.com - Buy Cheap Private Proxies Buy 50 Private Proxies Buy 100 Private Proxies Buy 200 Private Proxies Buy 500 Private Proxies Buy 1000 Private Proxies Buy 2000 Private Proxies ProxiesLive Proxies-free.com New Proxy Lists Every Day Proxies123