Update AuthorizationHelpers.cs

Author: localden

src/ModelContextProtocol.Core/Authentication/AuthorizationHelpers.cs

@@ -223,14 +223,13 @@ public async Task<IReadOnlyList<Uri>> GetAvailableAuthorizationServersAsync(
 
         try
         {
-            // Extract resource metadata behind the scenes
             var metadata = await ExtractProtectedResourceMetadata(response, serverUrl, cancellationToken);
-            return metadata.AuthorizationServers ?? new List<Uri>();
+            return metadata.AuthorizationServers ?? [];
         }
         catch (Exception ex)
         {
             _logger.LogError(ex, "Failed to get available authorization servers");
-            return new List<Uri>();
+            return [];
         }
     }
 }