Update dashboard-child-orgs.md (#5872)

Add missing limitation to note that variable values generated from a log search are populated using the parent organization.

Author: kevin-sumo

docs/dashboards/dashboard-child-orgs.md

@@ -81,6 +81,7 @@ If required, toggle off the **Include current variable values in the URL** optio
 
 - Public dashboards are not supported in MSSP environments.
 - Scheduled reports are only supported at the parent organization level, not for child orgs.
+- Variable values generated by Log Search are populated using the parent organization. 
 - Metrics and span queries are supported only at the parent organization level, not for child organizations.
 - Panels containing metrics or span queries will display no data if you switch from the parent organization to any child organization.
-- When exporting a dashboard at the child organization level, panels with metrics or span queries will also show no data.
+- When exporting a dashboard at the child organization level, panels with metrics or span queries will also show no data.