ruby/setup-ruby chooses version from .ruby-version

Author: hennevogel

.github/workflows/rubocop.yml

@@ -13,6 +13,5 @@ jobs:
       - uses: actions/checkout@v2
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: 3.1
           bundler-cache: true
       - run: bundle exec rubocop

.github/workflows/spec.yml

@@ -17,7 +17,6 @@ jobs:
       - uses: actions/checkout@v2
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: 3.1
           bundler-cache: true
       - name: Prepare spec
         run: |