Remove unused `fa_icon` helper method (#31511)

app/helpers/application_helper.rb

@@ -105,14 +105,6 @@ module ApplicationHelper
     policy(record).public_send(:"#{action}?")
   end
 
-  def fa_icon(icon, attributes = {})
-    class_names = attributes[:class]&.split || []
-    class_names << 'fa'
-    class_names += icon.split.map { |cl| "fa-#{cl}" }
-
-    content_tag(:i, nil, attributes.merge(class: class_names.join(' ')))
-  end
-
   def material_symbol(icon, attributes = {})
     inline_svg_tag(
       "400-24px/#{icon}.svg",

spec/helpers/application_helper_spec.rb

@@ -53,12 +53,6 @@ describe ApplicationHelper do
     end
   end
 
-  describe 'fa_icon' do
-    it 'returns a tag of fixed-width cog' do
-      expect(helper.fa_icon('cog fw')).to eq '<i class="fa fa-cog fa-fw"></i>'
-    end
-  end
-
   describe '#material_symbol' do
     it 'returns an svg with the icon and options' do
       expect(helper.material_symbol('lock', class: :test, data: { hidden: true }))