Fix build

Fix package validation by enabling roll-forward so that the lack of .NET 6 on the Ubuntu 24.04 runners isn't an issue.

.github/workflows/build.yml

@@ -129,7 +129,7 @@ jobs:
       env:
         DOTNET_VALIDATE_VERSION: ${{ needs.build.outputs.dotnet-validate-version }}
       run: |
-        dotnet tool install --global dotnet-validate --version ${env:DOTNET_VALIDATE_VERSION}
+        dotnet tool install --global dotnet-validate --version ${env:DOTNET_VALIDATE_VERSION} --allow-roll-forward
         $packages = Get-ChildItem -Filter "*.nupkg" | ForEach-Object { $_.FullName }
         $invalidPackages = 0
         foreach ($package in $packages) {