(CAT-2724) Add ruby_version input to acceptance and mend reusable workflows

[imaqsood]

Summary

module_ci.yml already accepts a ruby_version input, but module_acceptance.yml and mend_ruby.yml hardcoded ruby-version: "3.1". This adds the same input to those two reusable workflows so callers can select the Ruby version, defaulting to '3.1' to preserve current behaviour.

Jira: CAT-2724

Why

Puppet 9 modules require Ruby >= 3.2 at bundle time (facterdb ~> 3.1, Puppet 9 lint tooling). With Ruby pinned to 3.1, the acceptance Setup Test Matrix and the Mend jobs fail during bundle lock:

Bundler found conflicting requirements for the Ruby version:
  Ruby (>= 3.2.0)
  Current Ruby version:
    Ruby (= 3.1.7)

Changes

• module_acceptance.yml — add ruby_version input (default: '3.1'); use it in both ruby/setup-ruby steps (the setup_matrix job and the acceptance test job).
• mend_ruby.yml — add ruby_version input (default: '3.1'); use it in the setup-ruby step.

Default unchanged → existing callers unaffected. Puppet 9 modules opt in with ruby_version: "3.2".

Testing

Consumed from puppetlabs-inifile (MODULES-11703) pinned to this branch with ruby_version: "3.2":

• Acceptance Setup Test Matrix now bundles on Ruby 3.2 (previously failed on 3.1).
• Callers that don't set the input are unaffected (still Ruby 3.1).

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