Fix package downgrade warnings

Author: AArnott

Directory.Packages.props

@@ -33,8 +33,8 @@
     <PackageVersion Include="Nullable" Version="1.3.1" />
     <PackageVersion Include="System.Collections.Immutable" Version="8.0.0" />
     <PackageVersion Include="System.Memory" Version="4.6.0" />
-    <PackageVersion Include="System.Runtime.CompilerServices.Unsafe" Version="6.1.0" />
-    <PackageVersion Include="System.Threading.Tasks.Extensions" Version="4.6.0" />
+    <PackageVersion Include="System.Runtime.CompilerServices.Unsafe" Version="6.1.2" />
+    <PackageVersion Include="System.Threading.Tasks.Extensions" Version="4.6.3" />
     <PackageVersion Include="System.ValueTuple" Version="4.6.1" />
     <PackageVersion Include="xunit.v3.core.mtp-v2" Version="3.2.2" />
     <PackageVersion Include="Xunit.Combinatorial" Version="2.0.24" />

test/IsolatedTestHost/App.config

@@ -24,7 +24,7 @@ internal static class ReferencesHelper
         .WithNuGetConfigFilePath(NuGetConfigPath)
         .WithPackages(ImmutableArray.Create(
             new PackageIdentity("System.Collections.Immutable", "6.0.0"),
-            new PackageIdentity("System.Threading.Tasks.Extensions", "4.6.0"),
+            new PackageIdentity("System.Threading.Tasks.Extensions", "4.6.3"),
             new PackageIdentity("Microsoft.Bcl.AsyncInterfaces", "6.0.0")));
 
     internal static readonly ImmutableArray<string> VSSDKPackageReferences = ImmutableArray.Create(new string[]