CI: Drop boilerplate comments, use setup-ruby@v1

.github/workflows/ruby.yml

@@ -1,10 +1,3 @@
-# This workflow uses actions that are not certified by GitHub.
-# They are provided by a third-party and are governed by
-# separate terms of service, privacy policy, and support
-# documentation.
-# This workflow will download a prebuilt Ruby version, install dependencies and run tests with Rake
-# For more information see: https://github.com/marketplace/actions/setup-ruby-jruby-and-truffleruby
-
 name: Test
 
 on:
@@ -24,10 +17,7 @@ jobs:
     steps:
     - uses: actions/checkout@v2
     - name: Set up Ruby
-    # To automatically get bug fixes and new Ruby versions for ruby/setup-ruby,
-    # change this to (see https://github.com/ruby/setup-ruby#versioning):
-    # uses: ruby/setup-ruby@v1
-      uses: ruby/setup-ruby@473e4d8fe5dd94ee328fdfca9f8c9c7afc9dae5e
+      uses: ruby/setup-ruby@v1
       with:
         ruby-version: ${{ matrix.ruby-version }}
         bundler-cache: true # runs 'bundle install' and caches installed gems automatically