Enable Style/RedundantSelf RuboCop cop (#144)

Enables the `Style/RedundantSelf` cop in `RuboCop` configuration and
removes redundant self references in `UswdsFormBuilder#initialize`.

This cop helps maintain cleaner, more idiomatic Ruby code by flagging
unnecessary uses of `self.` In Ruby, explicit self is only required when
calling setter methods or disambiguating in specific contexts. Removing
redundant self references reduces visual noise and aligns with Ruby
community style conventions.

**References:**
https://docs.rubocop.org/rubocop/cops_style.html#styleredundantself 
https://rubystyle.guide/#no-self-unless-required

Author: giverm

template/{{app_name}}/.rubocop.yml

@@ -22,3 +22,5 @@ RSpecRails/HttpStatusNameConsistency:
 
 Style/FrozenStringLiteralComment:
   Enabled: true
+Style/RedundantSelf:
+  Enabled: true

template/{{app_name}}/app/helpers/uswds_form_builder.rb

@@ -10,8 +10,8 @@ class UswdsFormBuilder < ActionView::Helpers::FormBuilder
 
   def initialize(*args)
     super
-    self.options[:html] ||= {}
-    self.options[:html][:class] ||= "usa-form usa-form--large"
+    options[:html] ||= {}
+    options[:html][:class] ||= "usa-form usa-form--large"
   end
 
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