update to actions/checkout@v4

Author: seaxwi

.github/workflows/workflow-validate.yaml

@@ -16,7 +16,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v4
 
       - name: Markdownlint
         run: |
@@ -33,7 +33,7 @@ jobs:
       ZENDESK_PASS: ${{ secrets.ZENDESK_TOKEN }}
 
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v4
 
       - name: Preview changes
         run: |