fix(downstream-api-from-api-docs): Updates code snippet

Aims to replace the Obsoleted method call mentioned in the code snippet in Option 2 (call a downstream api):
- Using the existing code snippet when working with the latest Microsoft.Identity.Web package (v2.50) to use the updated (non-obsoleted) method.
- Not sure if this is definitely the right method to replace this with, or where else in the documentation this also might need updating, but it resolved the Obsoleted error message I was seeing when following the current guidance

Author: Issafalcon

articles/active-directory/develop/scenario-web-api-call-api-app-configuration.md

@@ -126,7 +126,7 @@ using Microsoft.Identity.Web;
 builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
     .AddMicrosoftIdentityWebApi(Configuration, "AzureAd")
     .EnableTokenAcquisitionToCallDownstreamApi()
-    .AddDownstreamWebApi("MyApi", Configuration.GetSection("GraphBeta"))
+    .AddDownstreamApi("MyApi", Configuration.GetSection("GraphBeta"))
     .AddInMemoryTokenCaches();
 // ...
 ```
@@ -228,4 +228,4 @@ For more information about the OBO protocol, see the [Microsoft identity platfor
 ## Next steps
 
 Move on to the next article in this scenario,
-[Acquire a token for the app](scenario-web-api-call-api-acquire-token.md).
+[Acquire a token for the app](scenario-web-api-call-api-acquire-token.md).