Revert "Use `secrets.GITHUB_TOKEN` instead of `PAT` for docs generation (#1377)" (#1378)

This reverts commit 1c80e535.

.github/workflows/update-documentation.yml

@@ -25,7 +25,7 @@ jobs:
       - name: Create a PR for Documentation
         id: push_image_info
         env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GITHUB_TOKEN: ${{ secrets.PAT }}
         run: |
           set -e
           echo "Start."