github-action: bump ruby/setup-ruby from 1.156.0 to 1.206.0

Bumps [ruby/setup-ruby](https://github.com/ruby/setup-ruby) from 1.156.0 to 1.206.0.
- [Release notes](https://github.com/ruby/setup-ruby/releases)
- [Changelog](https://github.com/ruby/setup-ruby/blob/master/release.rb)
- [Commits](ruby/setup-ruby@5cfe23c...bfefad8)

---
updated-dependencies:
- dependency-name: ruby/setup-ruby
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/test_on_pr.yml

@@ -56,7 +56,7 @@ jobs:
           go install github.com/alphagov/paas-cf/tools/pipecleaner@main
 
       - name: Install Ruby
-        uses: ruby/setup-ruby@5cfe23c062c0aac352e765b1b7cc12ea5255ccc4
+        uses: ruby/setup-ruby@bfefad842bb982ff05b233bcbc1571d97a87e69f
         with:
           ruby-version: "${{env.RUBY_VERSION}}"