Update actions/checkout action to v6 (#1478)

Author: mauroservienti-bot

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
       fail-fast: false
     steps:
       - name: Checkout
-        uses: actions/checkout@v5.0.1
+        uses: actions/checkout@v6.0.0
         with:
           fetch-depth: 0
       - name: Setup .NET SDK

.github/workflows/update-dependencies.yml

@@ -10,7 +10,7 @@ jobs:
       contents: read
     steps:
       - name: Checkout
-        uses: actions/checkout@v5.0.1
+        uses: actions/checkout@v6.0.0
       - name: Self-hosted Renovate
         uses: renovatebot/github-action@v44.0.3
         with: