chore(deps): update actions/checkout action to v6

Author: renovate-bot

.github/workflows/dotnet.yml

@@ -21,7 +21,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
           persist-credentials: false