Removed the un-neccessary attribute from msg create factory

spec/mailers/conversation_reply_mailer_spec.rb

@@ -15,7 +15,7 @@ RSpec.describe ConversationReplyMailer, type: :mailer do
     context 'with all mails' do
       let(:conversation) { create(:conversation, assignee: agent) }
       let(:message) { create(:message, conversation: conversation) }
-      let(:private_message) { create(:message, content: 'This is a private message', private: true, conversation: conversation) }
+      let(:private_message) { create(:message, content: 'This is a private message', conversation: conversation) }
       let(:mail) { described_class.reply_with_summary(message.conversation, Time.zone.now).deliver_now }
 
       it 'renders the subject' do