Use bundler-cache instead of bundle install

Author: hsbt

.github/workflows/test.yml

@@ -23,7 +23,6 @@ jobs:
       uses: ruby/setup-ruby@v1
       with:
         ruby-version: ${{ matrix.ruby }}
-    - name: Install dependencies
-      run: bundle install
+        bundler-cache: true
     - name: Run test
       run: bundle exec rake test