style(tests): using discard variable to signal intent

Author: cconstable

tests/Temporalio.Tests/Extensions/OpenTelemetry/TracingInterceptorTests.cs

@@ -916,7 +916,7 @@ private async Task<IReadOnlyCollection<Activity>> WithTracingWorkerAsync(
         var activities = new List<Activity>();
 
         // Setup provider
-        using var tracerProvider = global::OpenTelemetry.Sdk.CreateTracerProviderBuilder().
+        using var _ = global::OpenTelemetry.Sdk.CreateTracerProviderBuilder().
             AddSource(
                 TracingInterceptor.ClientSource.Name,
                 TracingInterceptor.WorkflowsSource.Name,