Bumping actions checkout to v6

Author: lamkina

.github/workflows/fprettify.yaml

@@ -12,7 +12,7 @@ jobs:
     timeout-minutes: ${{ inputs.TIMEOUT }}
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Set up Python
         uses: actions/setup-python@v6