Disable GetAsync_UnicodeHostName_SuccessStatusCodeInResponse (#37487)

SocketsHttpHandlerTest_HttpClientHandlerTest_Http2.GetAsync_UnicodeHostName_SuccessStatusCodeInResponse is periodically failing with TimeoutException. It seems to be caused by the target server unavailability, this PR disables the test until a new unicode test host is found.

src/libraries/Common/tests/System/Net/Http/HttpClientHandlerTest.cs

@@ -1625,6 +1625,7 @@ public async Task GetAsync_StatusCodeOutOfRange_ExpectedException(int statusCode
 
         [OuterLoop("Uses external server")]
         [Fact]
+        [ActiveIssue("https://github.com/dotnet/runtime/issues/29424")]
         public async Task GetAsync_UnicodeHostName_SuccessStatusCodeInResponse()
         {
             using (HttpClient client = CreateHttpClient())