Try upgrading(?) the GitHub action to fix the gh-pages build

Author: mpchadwick

.github/workflows/github-pages.yml

@@ -10,6 +10,6 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
-      - uses: helaili/jekyll-action@2.0.1
+      - uses: helaili/jekyll-action@v2
         env:
-          JEKYLL_PAT: ${{ secrets.JEKYLL_PAT }}
+          JEKYLL_PAT: ${{ secrets.JEKYLL_PAT }}