Rely on Barnes Railtie

Barnes auto boots up when running in Rails:

```
  class Railtie < ::Rails::Railtie
    config.barnes = {
      interval: DEFAULT_INTERVAL,
      panels:   DEFAULT_PANELS,
    }
    initializer 'barnes' do |app|
      Barnes.start(**config.barnes)
    end
  end
```

With the prior config, booting it showed it was running twice:

```
$ WEB_CONCURRENCY=2 bin/puma -C config/puma.rb
[66897] Puma starting in cluster mode...
...
== CALLED Barnes.start
/Users/rschneeman/.local/share/mise/installs/ruby/4.0.5/lib/ruby/gems/4.0.0/gems/barnes-1.0.0/lib/barnes/railtie.rb:42:in 'block in <class:Railtie>'
...
== CALLED Barnes.start
config/puma.rb:25:in 'block in Puma::DSL#_load_from'
/Users/rschneeman/.local/share/mise/installs/ruby/4.0.5/lib/ruby/gems/4.0.0/gems/puma-8.0.1/lib/puma/configuration.rb:356:in 'block in Puma::Configuration#run_hooks'
```

Author: schneems

config/puma.rb

@@ -17,10 +17,7 @@
 plugin :tmp_restart
 
 before_fork do
-  require "barnes"
   require "puma_worker_killer"
 
   PumaWorkerKiller.enable_rolling_restart # Default is every 6 hours
-
-  Barnes.start
 end