gha: pin actions/checkout to hash for v6.0.0 (#65)

actions/checkout@1af3b93

Author: jbampton

.github/workflows/build-pelican.yml

@@ -16,7 +16,7 @@ jobs:
     permissions:
       contents: write   # because we push to asf-site
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3  # v6.0.0
         with:
           persist-credentials: true
           ref: ${{ github.ref || 'main' }}

.github/workflows/pre-commit.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3  # v6.0.0
         with:
           persist-credentials: false
       - name: Install