Fixes build warning

Author: dnperfors

test/HttpClientTestHelpers.Tests/TestableHttpMessageHandlerTests.cs

@@ -193,7 +193,7 @@ public async Task SimulateTimout_WhenRequestIsMade_ThrowsTaskCancelationExceptio
             sut.SimulateTimeout();
             using var client = new HttpClient(sut);
 
-            var exception = await Assert.ThrowsAsync<TaskCanceledException>(() => client.GetAsync("https://example.com"));
+            var exception = await Assert.ThrowsAsync<TaskCanceledException>(() => client.GetAsync(new Uri("https://example.com")));
             Assert.Equal(new OperationCanceledException().Message, exception.Message);
         }
     }