Upgrade Ruby in the github actions

Author: rafaelfranca

.github/workflows/rubocop.yml

@@ -11,7 +11,7 @@ jobs:
     - name: Set up Ruby 2.6
       uses: actions/setup-ruby@v1
       with:
-        ruby-version: 2.6.x
+        ruby-version: 2.7.x
     - name: Install required package
       run: |
         sudo apt-get update