Clarifies the availability of dormant user feature

In order to reduce confusion around the state of the dormant member
feature, this commit updates the docs to be more clear.

Changelog: changed

doc/user/group/moderate_users.md

@@ -73,7 +73,7 @@ DETAILS:
 FLAG:
 The availability of this feature is controlled by a feature flag.
 For more information, see the history.
-This feature is available for testing, but not ready for production use.
+This feature is currently in development and not ready for production use.
 
 Prerequisites: