Flaky tests (#31502)

Author: John Luo

src/Servers/Kestrel/Core/test/AsciiDecoding.cs

@@ -5,6 +5,7 @@
 using System.Linq;
 using System.Numerics;
 using Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Infrastructure;
+using Microsoft.AspNetCore.Testing;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
@@ -110,6 +111,7 @@ private void DifferentLengthsAreNotEqual()
         }
 
         [Fact]
+        [QuarantinedTest("https://github.com/dotnet/aspnetcore/issues/31500")]
         private void AsciiBytesEqualAsciiStrings()
         {
             var byteRange = Enumerable.Range(1, 127).Select(x => (byte)x);

src/Servers/Kestrel/test/InMemory.FunctionalTests/Http3/Http3StreamTests.cs

@@ -1623,6 +1623,7 @@ await requestStream.WaitForStreamErrorAsync(
         }
 
         [Fact]
+        [QuarantinedTest("https://github.com/dotnet/aspnetcore/issues/31501")]
         public async Task DataBeforeHeaders_UnexpectedFrameError()
         {
             var requestStream = await InitializeConnectionAndStreamsAsync(_noopApplication);