Add info to docs about concurrent session limits (#31333)

* Add info to docs about concurrent session limits

This parallels a [change in the Grafana Cloud docs](https://github.com/grafana/website/pull/3504) which was based on a kind and appreciated message from support. The limit does not apply to Grafana OSS, just to Enterprise and Cloud, as far as any of us know.

* Update docs/sources/enterprise/license-restrictions.md

Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

docs/sources/enterprise/license-restrictions.md

@@ -25,6 +25,8 @@ Restrictions are applied separately for viewers and editors.
 
 When the number of maximum active viewers or editors is reached, Grafana displays a warning banner.
 
+Sometimes it is useful to log in to an account from multiple locations concurrently. With Grafana Enterprise, accounts are limited to three concurrent sessions.
+
 ## Expiration date
 
 The license expiration date is the date when a license is no longer active. As the license expiration date approaches, Grafana Enterprise displays a banner.