updates tests to reflect changes made to email body

Author: Kneeba921

spec/mailers/better_together/conversation_mailer_spec.rb

@@ -17,15 +17,14 @@ module BetterTogether
       end
 
       it 'renders the headers' do
-        expect(mail.subject).to eq("New message in conversation \"#{conversation.title}\"")
+        expect(mail.subject).to have_content('conversation has an unread message')
         expect(mail.to).to include(recipient.email)
         expect(mail.from).to include('[email protected]')
       end
 
       it 'renders the body' do
         expect(mail.body.encoded).to have_content("Hello #{recipient.person.name}")
-        expect(mail.body.encoded).to have_content("#{sender.person.name}:")
-        expect(mail.body.encoded).to have_content(message.content.to_plain_text)
+        expect(mail.body.encoded).to have_content("You have an unread message from #{sender.person.name}:")
       end
 
       it 'sends a message notification email' do