ci: pin ruby/setup-ruby

Author: nschonni

.github/workflows/licensed.yml

@@ -16,7 +16,7 @@ jobs:
       - uses: actions/checkout@v3
         with:
           fetch-depth: 0 # prefer to use a full fetch for licensed workflows
-      - uses: ruby/setup-ruby@v1
+      - uses: ruby/setup-ruby@28c4deda893d5a96a6b2d958c5b47fc18d65c9d3 # v1.213.0
         with:
           ruby-version: ruby
       - uses: github/setup-licensed@v1