Update actions/checkout digest to df4cb1c (#39321)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

.github/workflows/lint-css.yml

@@ -31,7 +31,7 @@ jobs:
 
     steps:
       - name: Clone repository
-        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
+        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
 
       - name: Set up Javascript environment
         uses: ./.github/actions/setup-javascript