Add role-specific user fabricators (#33437)

spec/policies/status_policy_spec.rb

@@ -5,7 +5,7 @@ require 'rails_helper'
 RSpec.describe StatusPolicy, type: :model do
   subject { described_class }
 
-  let(:admin) { Fabricate(:user, role: UserRole.find_by(name: 'Admin')) }
+  let(:admin) { Fabricate(:admin_user) }
   let(:alice) { Fabricate(:account, username: 'alice') }
   let(:bob) { Fabricate(:account, username: 'bob') }
   let(:status) { Fabricate(:status, account: alice) }