Redis modules and blocking commands - clarify if this is still experimental / was implemented

[simonprickett]

The blocking feature described at: https://redis.io/docs/reference/modules/modules-blocking-ops/

is documented as experimental and:

There is no ETA for this feature but it may appear in the course of the Redis 4.0 release at some point.

We're now at Redis 7. This page should be updated to say whether this is still experimental and reviewed in case the API changed since this page was written.