Add beaker-puppet constraint to sync.yml

In a878ab1, we limited beaker-puppet to Ruby <= 3.1. This commit adds
that restriction to .sync.yml so that change will persist across PDK
updates, and adds a comment with the rationale behind this restriction.

Author: mhashizume

.sync.yml

@@ -33,9 +33,11 @@ Gemfile:
         from_env: BEAKER_HOSTGENERATOR_VERSION
       - gem: beaker-rspec
         from_env: BEAKER_RSPEC_VERSION
+      # Prevent beaker-puppet from being installed on Ruby > 3.1 until beaker-puppet supports newer Rubies
       - gem: beaker-puppet
         from_env: BEAKER_PUPPET_VERSION
         version: '~> 3.0'
+        condition: Gem::Requirement.create('< 3.1.0').satisfied_by?(Gem::Version.new(RUBY_VERSION.dup))
       - gem: async
         version: '~> 1'
       - gem: beaker-module_install_helper