Bump actions/checkout action to v6 (#155)

Author: renovate[bot]

.github/workflows/build.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-24.04
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       # - name: Setup GHPR
       #   run: dotnet nuget add source -u ${{ github.repository_owner }} -p ${{ secrets.GITHUB_TOKEN }}
       #     --store-password-in-clear-text -n github "https://nuget.pkg.github.com/${{ github.repository_owner }}/index.json"