fix: pin actions/checkout to a specific hash

Updated the checkout action reference to use a specific commit hash to
ensure build reproducibility and improve security.

Author: chmouel

.github/workflows/e2e.yaml

@@ -313,7 +313,7 @@ jobs:
           echo "${HOME}/go/bin" >> "$GITHUB_PATH"
 
       - name: Clone startpaac
-        uses: actions/checkout@v6
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
         with:
           repository: openshift-pipelines/startpaac
           path: startpaac