Update data-retention-overview.md

Added the below under Important (How it works):
> - Customers that bring own key (BYOK), note that long term retained data in the Dataverse managed data lake is encrypted with Microsoft managed key only.

Author: pnghub

powerapps-docs/maker/data-platform/data-retention-overview.md

@@ -49,6 +49,7 @@ Application admins set up custom policies for a table with criterion to retain d
 
 > [!IMPORTANT]
 > - Once data is retained in the Dataverse long term (inactive) store it can't be moved back to the Dataverse live (active) data store.
+> - Customers that bring own key (BYOK), note that long term retained data in the Dataverse managed data lake is encrypted with Microsoft managed key only.
 > - When a retention policy is run, the process makes API requests in Microsoft Power Platform. These requests are counted towards the existing API requests available with your plan. More information: [Requests limits and allocations](/power-platform/admin/api-request-limits-allocations)
 
 Dataverse provides read-only access to the retained data via: