ci: replace GHPAGES_DEPLOY_KEY with MY_REPO_PAT for Pages deployment

peaceiris/actions-gh-pages deploy_key blocked by mazduino org policy.
Switch to personal_token using MY_REPO_PAT so gh-pages branch can be
created and INI files deployed on first nightly run.

Author: amrikarisma

.github/workflows/nightly-release.yaml

@@ -169,7 +169,7 @@ jobs:
       - name: Deploy INI files to GitHub Pages
         uses: peaceiris/actions-gh-pages@v3
         with:
-          deploy_key: ${{ secrets.GHPAGES_DEPLOY_KEY }}
+          personal_token: ${{ secrets.MY_REPO_PAT }}
           publish_dir: ./ini-pages
           destination_dir: ini
           keep_files: true