Update .github/workflows/backport.yml

Co-authored-by: Daijiro Fukuda <[email protected]>

Author: kenhys

.github/workflows/backport.yml

@@ -29,8 +29,7 @@ jobs:
         uses: ruby/setup-ruby@8aeb6ff8030dd539317f8e1769a044873b56ea71 # v1.268.0
         with:
           ruby-version: ${{ matrix.ruby-version }}
-      - name: Install dependencies
-        run: bundle install
+          bundler-cache: true
       - name: Run Benchmark
         shell: bash
         run: |