fix: Add missing CSAT URL in email reply templates (#11808)

As part of PR [#11622](https://github.com/chatwoot/chatwoot/pull/11622),
we intentionally hide CSAT survey URLs from agents in the dashboard to
avoid exposing those links internally. However, email replies being
external communications to contacts should still include the survey
URLs.

We missed handling that specific case for email channels. All other
external channels like WhatsApp, Instagram, Telegram, etc., were already
working correctly and continue to include the survey URLs as intended.

---------

Co-authored-by: Pranav <pranav@chatwoot.com>

app/views/mailers/conversation_reply_mailer/email_reply.html.erb

@@ -1,5 +1,5 @@
 <% if @message.content %>
-  <%= ChatwootMarkdownRenderer.new(@message.content).render_message %>
+  <%= ChatwootMarkdownRenderer.new(@message.outgoing_content).render_message %>
 <% end %>
 <% if @large_attachments.present? %>
   <p>Attachments:</p>