Bump actions/upload-artifact from 5 to 6 (#141)

Author: dependabot[bot]

.github/workflows/dotnet.yaml

@@ -151,7 +151,7 @@ jobs:
     - name: Pack
       run: nix develop --command dotnet pack --configuration Release
     - name: Upload NuGet artifact
-      uses: actions/upload-artifact@v5
+      uses: actions/upload-artifact@v6
       with:
         name: nuget-package
         path: WoofWare.DotnetRuntimeLocator/bin/Release/WoofWare.DotnetRuntimeLocator.*.nupkg