Fix identity type in command

This PR fixes a small inconsistency in the commands. Before the change, both commands the, the user as well as the system-assigned identity are referring to system identity. That was confusing to me while following the tutorial.

Author: Freshchris01

articles/app-service/tutorial-connect-msi-azure-database.md

@@ -237,7 +237,7 @@ Next, you configure your App Service app to connect to SQL Database with a manag
 
     ```sql
     SET aad_validate_oids_in_tenant = off;
-    CREATE ROLE <postgresql-user-name> WITH LOGIN PASSWORD '<application-id-of-system-assigned-identity>' IN ROLE azure_ad_user;
+    CREATE ROLE <postgresql-user-name> WITH LOGIN PASSWORD '<application-id-of-user-assigned-identity>' IN ROLE azure_ad_user;
     ```
 
     Whatever name you choose for *\<postgresql-user-name>*, it's the PostgreSQL user you'll use to connect to the database later from your code in App Service.