add missing package (#48654)

Author: gewarren

docs/ai/quickstarts/generate-images.md

@@ -47,6 +47,7 @@ Complete the following steps to create a .NET console app to connect to an AI mo
 
     ```bash
     dotnet add package Azure.AI.OpenAI
+    dotnet add package Azure.Identity
     dotnet add package Microsoft.Extensions.Configuration
     dotnet add package Microsoft.Extensions.Configuration.UserSecrets
     ```