Replace actions/setup-ruby with ruby/setup-ruby

Author: jigarius

.github/workflows/validation.yml

@@ -7,7 +7,7 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - name: Install Ruby
-        uses: actions/setup-ruby@v1
+        uses: ruby/setup-ruby@v1
         with:
           ruby-version: '2.6'
       - name: Install gems