Add role-specific user fabricators (#33437)

spec/system/admin/account_moderation_notes_spec.rb

@@ -3,7 +3,7 @@
 require 'rails_helper'
 
 RSpec.describe 'Admin::AccountModerationNotes' do
-  let(:current_user) { Fabricate(:user, role: UserRole.find_by(name: 'Admin')) }
+  let(:current_user) { Fabricate(:admin_user) }
   let(:target_account) { Fabricate(:account) }
 
   before { sign_in current_user }