[wasm] Fix Wasm.Build.Tests on main (#92741)

* CI: Don't include ref pack when the tests need workload

.. as it already includes it.

#92732 broke this as a
side-effect which caused the `microsoft.netcore.app.ref` directory to
not be created.

Fixes #92732 .

* [wasm] WBT: Update skiasharp reference

`blz_deploy_on_build_Debug_True_npl3f0nk_qee.csproj : error NU1903: Package 'SkiaSharp' 2.88.4-preview.76 has a known high severity vulnerability`

src/libraries/sendtohelixhelp.proj

@@ -270,8 +270,6 @@
     <ItemGroup Condition="'$(NeedsWorkload)' == 'true'">
       <HelixCorrelationPayload Include="$(SdkWithWorkloadForTestingPath)"     Destination="$(SdkForWorkloadTestingDirName)" Condition="'$(TestUsingWorkloads)' == 'true'" />
       <HelixCorrelationPayload Include="$(SdkWithNoWorkloadForTestingPath)"   Destination="$(SdkForWorkloadTestingDirName)" Condition="'$(TestUsingWorkloads)' != 'true'" />
-
-      <HelixCorrelationPayload Include="$(MicrosoftNetCoreAppRefPackDir)"     Destination="microsoft.netcore.app.ref" />
     </ItemGroup>
 
     <ItemGroup>

src/mono/wasm/Wasm.Build.Tests/BuildTestBase.cs

@@ -599,8 +599,8 @@ internal BuildPaths GetBuildPaths(BuildArgs buildArgs, bool forPublish = true)
         }
 
         protected static string GetSkiaSharpReferenceItems()
-            => @"<PackageReference Include=""SkiaSharp"" Version=""2.88.4-preview.76"" />
-                <PackageReference Include=""SkiaSharp.NativeAssets.WebAssembly"" Version=""2.88.4-preview.76"" />
+            => @"<PackageReference Include=""SkiaSharp"" Version=""2.88.6"" />
+                <PackageReference Include=""SkiaSharp.NativeAssets.WebAssembly"" Version=""2.88.6"" />
                 <NativeFileReference Include=""$(SkiaSharpStaticLibraryPath)\3.1.34\st\*.a"" />";
 
         protected static string s_mainReturns42 = @"