Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/sync-labels.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - name: Run Labeler
         if: success()
         uses: crazy-max/ghaction-github-labeler@v5

.github/workflows/test-self-hosted.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: self-hosted
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - name: test
         run: echo "Test"
       - name: test