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

Author: renovate[bot]

.github/workflows/nightly.yaml

@@ -19,7 +19,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Remove existing nightly tag
         run: |
@@ -51,7 +51,7 @@ jobs:
             }
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Get version info
         id: version