[Wasm.Build.Tests] Fixup wildcard matching for runtime packs (#85286)

The naming is
`Microsoft.NETCore.App.Runtime.Mono.{variant}.{rid}.{version}.nupkg`

Fixes local WBT builds for non-default runtime variants (eg: build
with `/p:MonoWasmBuildVariant=multithread` then run WBT)

eng/testing/tests.browser.targets

@@ -286,7 +286,7 @@
     </PropertyGroup>
 
     <ItemGroup>
-      <_RuntimePackNugetAvailable Include="$(LibrariesShippingPackagesDir)Microsoft.NETCore.App.Runtime.Mono.$(RuntimeIdentifier).*$(PackageVersionForWorkloadManifests).nupkg" />
+      <_RuntimePackNugetAvailable Include="$(LibrariesShippingPackagesDir)Microsoft.NETCore.App.Runtime.Mono.*.$(RuntimeIdentifier).*$(PackageVersionForWorkloadManifests).nupkg" />
       <_RuntimePackNugetAvailable Remove="@(_RuntimePackNugetAvailable)" Condition="$([System.String]::new('%(_RuntimePackNugetAvailable.FileName)').EndsWith('.symbols'))" />
     </ItemGroup>