fix security in ci-jobs

Author: glesur

.github/workflows/idefix-ci-jobs.yml

@@ -231,9 +231,10 @@ jobs:
     runs-on: self-hosted
     steps:
       - name: Check out repo
-        uses: actions/checkout@v3
+        uses: actions/checkout@f43a0e5ff2bd294095638e18286ca9a3d1956744 # v3.6.0
         with:
           submodules: recursive
+          persist-credentials: false
       - name: Restart dumps
         run: scripts/ci/run-tests $IDEFIX_DIR/test/IO/dump -all $TESTME_OPTIONS
       - name: Pydefix