Change link to community drivers
Change link to community drivers

Came across this dead link in the docs.
Looks like [rethinkdb/rethinkdb](https://github.com/rethinkdb/rethinkdb/wiki/) doesn't have a wiki enabled anymore.
rust-rethinkdb/reql,rust-rethinkdb/reql,rust-rethinkdb/reql,rust-rethinkdb/reql,rust-rethinkdb/reql,rust-rethinkdb/reql