chore: Update auto-publish.yml: Use actions/checkout@v4

Author: plehegar

.github/workflows/auto-publish.yml

@@ -12,7 +12,7 @@ jobs:
     name: Validate and Publish
     runs-on: ubuntu-latest # only linux supported at present
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: w3c/spec-prod@v2
         with:
           TOOLCHAIN: respec