Bump actions/upload-artifact from 5 to 6 (#135)

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 5 to 6.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v5...v6)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/dotnet.yaml

@@ -94,7 +94,7 @@ jobs:
       - name: Pack
         run: dotnet pack ApiSurface/ApiSurface.fsproj --configuration Release
       - name: Upload NuGet artifact
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: nuget-package
           path: ApiSurface/bin/Release/ApiSurface.*.nupkg