Update auto-publish.yml (#204)

Update to use ubuntu-latest to hopefully fix spec-prod runs

Author: mkruisselbrink

.github/workflows/auto-publish.yml

@@ -7,7 +7,7 @@ on:
 jobs:
   main:
     name: Build, Validate and Deploy
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
       - uses: w3c/spec-prod@v2