[codex] Pin GitHub Actions workflow references (#2558)

Author: hintz-openai

.github/workflows/stale.yaml

@@ -7,7 +7,7 @@ jobs:
   stale:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/stale@v8
+      - uses: actions/stale@1160a2240286f5da8ec72b1c0816ce2481aabf84 # v8
         with:
           stale-issue-message: "This issue is stale because it has been open 60 days with no activity. Remove stale label or comment or this will be closed in 10 days."
           stale-pr-message: "This PR is stale because it has been open 60 days with no activity. Remove stale label or comment or this will be closed in 10 days."

.github/workflows/validate-notebooks.yaml

@@ -9,12 +9,12 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v3
+        uses: actions/checkout@f43a0e5ff2bd294095638e18286ca9a3d1956744 # v3
         with:
           fetch-depth: 0  # needed for git diff to work
 
       - name: Set up Python
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@7f4fc3e22c37d6ff65e88745f38bd3157c663f7c # v4
         with:
           python-version: '3.12'