Add 'head' to ruby-version matrix and turn off fail-fast in CI workflow

[wwahammy]

No description provided.

[yukideluxe]

@wwahammy head doesn't seem to be working because the tsort gem must be added to the Gemfile. If you tweak it, I will approve! 😊

/home/runner/.rubies/ruby-head/lib/ruby/gems/4.1.0+1/gems/railties-7.0.10/lib/rails/initializable.rb:3: warning: tsort used to be loaded from the standard library, but is not part of the default gems since Ruby 4.1.0.
You can add tsort to your Gemfile or gemspec to fix this error.

[wwahammy]

@yukideluxe I think it'll be good now but I can't run the workflows myself.

[yukideluxe]

Thanks!