It's supposed to be faster and more compact, and the previous format
will become unsupported in Rails 7.2 as per Rails boot warnings:
> DEPRECATION WARNING: Support for `config.active_support.cache_format_version = 6.1` has been deprecated and will be removed in Rails 7.2.
>
> Check the Rails upgrade guide at https://guides.rubyonrails.org/upgrading_ruby_on_rails.html#new-activesupport-cache-serialization-format
> for more information on how to upgrade.
> (called from <main> at /path/to/config/environment.rb:5)
