Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/preview.yml

@@ -25,7 +25,7 @@ jobs:
           fi
 
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - uses: pnpm/action-setup@v3.0.0
         with:

.github/workflows/production.yml

@@ -24,7 +24,7 @@ jobs:
           fi
 
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - uses: pnpm/action-setup@v3.0.0
         with:

.github/workflows/sync-branches.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: 🛎 Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: "0"
       - name: 🪪 Set git name+email