Enable System.Text.Json tests for Wasm AOT (#54833)

Author: lewing

src/libraries/tests.proj

@@ -283,9 +283,6 @@
 
     <!-- Issue: https://github.com/dotnet/runtime/issues/52393 -->
     <ProjectExclusions Include="$(MSBuildThisFileDirectory)System.Runtime/tests/System.Runtime.Tests.csproj" />
-
-    <!-- Issue: https://github.com/dotnet/runtime/issues/51961 -->
-    <ProjectExclusions Include="$(MSBuildThisFileDirectory)System.Text.Json/tests/System.Text.Json.Tests/System.Text.Json.Tests.csproj" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetOS)' == 'Browser' and '$(BuildAOTTestsOnHelix)' == 'true' and '$(RunDisabledWasmTests)' != 'true'">