Update link to open registration homeservers with a maintained list #73
Description
https://about.riot.im/free currently links to "free servers open for public registration", which is a link to https://www.hello-matrix.net/public_servers.php. However this list is maintained (don't let the last-updated bit at the bottom fool you, stats aren't actually being updated).
We should probably link to a different page, or curate our own list like https://joinmastodon.org/ does.