Update set-up-api-center.md

Name must be unique in region

Author: dlepow

articles/api-center/set-up-api-center.md

@@ -42,7 +42,7 @@ If you haven't already, you need to register the **Microsoft.ApiCenter** resourc
 
     1. Select an existing resource group, or select **New** to create a new one. 
 
-    1. Enter a **Name** for your API center. It must be unique in your subscription. 
+    1. Enter a **Name** for your API center. It must be unique in the region where you're creating your API center. 
 
     1. In **Region**, select one of the [available regions](overview.md#available-regions) for API Center preview.