Update cross-workspace-queries.md

Adding a note to callout that we should use workspace identifiers vs the workspace name as per the same guidance as:
https://learn.microsoft.com/en-us/azure/azure-monitor/logs/workspace-expression

Author: josecons-msft

articles/azure-monitor/logs/api/cross-workspace-queries.md

@@ -21,6 +21,9 @@ For either implicit or explicit cross-workspace queries, you need to specify the
  - Workspace ID - GUID string
  - Azure Resource ID - string with format /subscriptions/\<subscriptionId\>/resourceGroups/\<resourceGroup\>/providers/  microsoft.operationalinsights/workspaces/\<workspaceName\>
 
+> [!NOTE]
+> We strongly recommend identifying a workspace by its unique Workspace ID or Azure Resource ID because they remove ambiguity and are more performant.
+
 ## Implicit cross workspace queries
 
 For implicit syntax, specify the workspaces that you want to include in your query scope. The API performs a single query over each application provided in your list. The syntax for a cross-workspace POST is: