Pin to exact GH actions, preventing ACE in CI

Also updates actions.

.github/workflows/monthly-nightly-update.yml

@@ -9,7 +9,7 @@ jobs:
     name: Update nightly
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac
         with:
           submodules: "recursive"
 
@@ -28,7 +28,7 @@ jobs:
           git push -u origin $(date +"nightly-%Y-%m")
 
       - name: Pull Request
-        uses: actions/github-script@v6
+        uses: actions/github-script@d7906e4ad0b1822421a7e6a35d5ca353c962f410
         with:
           script: |
             const { repo, owner } = context.repo;