Remove redundant bundle install in CI

Author: mallowlabs

.github/workflows/ci.yml

@@ -15,7 +15,4 @@ jobs:
       - uses: ruby/setup-ruby@v1
         with:
           bundler-cache: true
-      - run: bundle install --jobs 4 --retry 3
-        env:
-          BUNDLE_PATH: vendor/bundle
       - run: bundle exec jekyll build