Remove helper not used anymore because lexical handles it

https://github.com/basecamp/actiontext-lexical/pull/18

app/helpers/application_helper.rb

@@ -6,8 +6,4 @@ module ApplicationHelper
   def icon_tag(name, **options)
     tag.span class: class_names("icon icon--#{name}", options.delete(:class)), "aria-hidden": true, **options
   end
-
-  def filterable_name(text)
-    I18n.transliterate(text.to_s).downcase
-  end
 end

app/views/prompts/collections/users/_user.html.erb

@@ -1,4 +1,4 @@
-<lexical-prompt-item search="<%= "#{filterable_name(user.name)} #{user.initials}" %>" sgid="<%= user.attachable_sgid %>">
+<lexical-prompt-item search="<%= "#{user.name} #{user.initials}" %>" sgid="<%= user.attachable_sgid %>">
   <template type="menu">
     <%= avatar_image_tag user %>
     <%= user.name %>