Add suggestion for the use of newer Azure.Identity for token chaching

While Azure.Identity 1.8 isn’t the most recent version, quite a few customers continue to use Azure.Identity 1.7 or earlier versions. Sometimes, these customers encounter port exhaustion issues when they switch their app’s authentication method from SQL Server authentication to Managed Identity referring to this document.

Author: hihayak

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

@@ -172,6 +172,9 @@ The steps you follow for your project depends on whether you're using [Entity Fr
     Install-Package Azure.Identity
     Update-Package EntityFramework
     ```
+    > [!NOTE]
+    > The token caching feature for Managed Identity is available starting from Azure.Identity version 1.8.0. To help reduce network port usage, consider updating Azure.Identity to this version or later.
+    
 1. In your DbContext object (in *Models/MyDbContext.cs*), add the following code to the default constructor.
 
     ```csharp