fixes release workflow

Author: Sherry520

.github/workflows/release-on-merge.yml

@@ -27,7 +27,7 @@ jobs:
         bundler-cache: true # runs 'bundle install' and caches installed gems automatically
 
     - name: Build release assets
-      run: bundle exec rake book:build_build
+      run: bundle exec rake book:build
 
     - name: Create release
       uses: ncipollo/release-action@v1