[wasm] Bump the stj version to avoid error (#104751)

* Bump the stj version to avoid error

* System.Net.Http.Json does not have version 8.0.4, changing to net9 prev 5

---------

Co-authored-by: Ilona Tomkowicz <32700855+ilonatommy@users.noreply.github.com>

Author: lewing

src/mono/wasm/testassets/WasmOnAspNetCore/Shared/Shared.csproj

@@ -10,7 +10,7 @@
 
   <!-- versions are pinned but when run from WBT level, it's taking in-tree runtime -->
   <ItemGroup>
-    <PackageReference Include="System.Net.Http.Json" Version="8.0.0" />
+    <PackageReference Include="System.Net.Http.Json" Version="9.0.0-preview.5.24306.7" />
     <PackageReference Include="Microsoft.AspNetCore.SignalR.Client" Version="9.0.0-preview.5.24306.11" />
   </ItemGroup>
 </Project>