CI: use bundler-cache from ruby/setup-ruby

.github/workflows/ci.yml

@@ -16,26 +16,24 @@ jobs:
 
     steps:
       - uses: actions/checkout@v2
-      - uses: actions/setup-ruby@v1
+      - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: 2.7.x
-      - name: Install dependencies
-        run: bundle install
+          ruby-version: 2.7
+          bundler-cache: true 
       - name: Run rubocop
         run: bundle exec rubocop --format progress
   build:
     needs: [linting]
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby: ['2.5.x', '2.6.x', '2.7.x']
+        ruby: ['2.5', '2.6', '2.7']
 
     steps:
       - uses: actions/checkout@v2
-      - uses: actions/setup-ruby@v1
+      - uses: ruby/setup-ruby@v1
         with:
           ruby-version: ${{ matrix.ruby }}
-      - name: Install dependencies
-        run: bundle install
+          bundler-cache: true
       - name: Run tests
         run: bundle exec rake