Update actions/checkout action to v6

.gitea/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
     name: Validate templates
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
 
       - name: Setup Terraform
         uses: hashicorp/setup-terraform@v2
@@ -38,7 +38,7 @@ jobs:
       COMMIT_SHORT_SHA: ${{ github.sha }}
       REPO: ${{ github.repository }}
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
 
       - name: Install Coder CLI
         run: |