Fix deploy step.

.github/workflows/ci.yml

@@ -43,10 +43,10 @@ jobs:
         # Only run on main branch push (e.g. pull request merge).
         if: github.event_name == 'push'
         run: |
-          git config --global user.name "${{ env.CI_COMMIT_AUTHOR }}"
+          git config --global user.name "Deployer"
           git config --global user.email "username@users.noreply.github.com"
           git add --force book/book
-          git commit -m "${{ env.CI_COMMIT_MESSAGE }}"
+          git commit -m "Render book"
           git push --set-upstream --force-with-lease origin deploy
 
   formatter: