[CP-Sec] Pin actions/checkout version to hash

Author: carlewis

.github/workflows/check_clang_format.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-20.04
     steps:
       - name: Code checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332 # v4.1.7
       - name: Is-clang-formatted hook
         run:  ./hooks/is-clang-formatted.sh
       - name: Show diff