Try github version of ruby-setup action

.github/workflows/unit-tests.yml

@@ -22,7 +22,7 @@ jobs:
     - 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: actions/setup-ruby@v1
       with:
         ruby-version: ${{ matrix.ruby-version }}
         bundler-cache: true # runs 'bundle install' and caches installed gems automatically