Up[date actions/checkout to use v4

Author: plehegar

.github/workflows/auto-publish.yml

@@ -8,7 +8,7 @@ jobs:
     name: Build, Validate and Deploy
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: w3c/spec-prod@v2
         with:
           W3C_ECHIDNA_TOKEN: ${{ secrets.W3C_TR_TOKEN_L2 }}