Update actions-gh-pages step: v3 -> v4

Author: yasulab

.github/workflows/deploy_to_pages.yml

@@ -46,7 +46,7 @@ jobs:
 
     - name: 🚀 Deploy to GitHub Pages
       if:   github.ref == 'refs/heads/main' && job.status == 'success'
-      uses: peaceiris/actions-gh-pages@v3
+      uses: peaceiris/actions-gh-pages@v4
       with:
         personal_token: ${{ secrets.GITHUB_TOKEN }}
         publish_dir:    ./_site

.github/workflows/scheduler_daily.yml

@@ -100,7 +100,7 @@ jobs:
 
     - name: 🚀 Deploy to GitHub Pages
       if:   github.ref == 'refs/heads/main' && job.status == 'success'
-      uses: peaceiris/actions-gh-pages@v3
+      uses: peaceiris/actions-gh-pages@v4
       with:
         personal_token: ${{ secrets.GITHUB_TOKEN }}
         publish_dir:    ./_site