Merge pull request rails#44871 from timchaston/fix-broken-link-for-redis-pub-sub-in-action-cable-overview

Fix broken link for Redis PubSub in 'Action Cable Overview' guide [ci-skip]

Author: jonathanhefner

guides/source/action_cable_overview.md

@@ -721,7 +721,7 @@ The async adapter is intended for development/testing and should not be used in
 
 The Redis adapter requires users to provide a URL pointing to the Redis server.
 Additionally, a `channel_prefix` may be provided to avoid channel name collisions
-when using the same Redis server for multiple applications. See the [Redis PubSub documentation](https://redis.io/topics/pubsub#database-amp-scoping) for more details.
+when using the same Redis server for multiple applications. See the [Redis Pub/Sub documentation](https://redis.io/docs/manual/pubsub/#database--scoping) for more details.
 
 The Redis adapter also supports SSL/TLS connections. The required SSL/TLS parameters can be passed in `ssl_params` key in the configuration YAML file.