Fix HttpStress build (#72601)

src/libraries/System.Net.Http/tests/StressTests/HttpStress/StressClient.cs

@@ -54,9 +54,14 @@ HttpMessageHandler CreateHttpHandler()
                 }
                 else
                 {
-                    SocketsHttpHandler handler = CreateSocketsHttpHandler(allowAllCertificates: true);
-                    handler.PooledConnectionLifetime = _config.ConnectionLifetime.GetValueOrDefault(Timeout.InfiniteTimeSpan);
-                    return handler;
+                    return new SocketsHttpHandler()
+                    {
+                        PooledConnectionLifetime = _config.ConnectionLifetime.GetValueOrDefault(Timeout.InfiniteTimeSpan),
+                        SslOptions = new SslClientAuthenticationOptions
+                        {
+                            RemoteCertificateValidationCallback = delegate { return true; }
+                        }
+                    };
                 }
             }