fix: Use commonmarker instead of redcarpet (#1732)

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

@@ -1,4 +1,3 @@
-<% markdown = Redcarpet::Markdown.new(Redcarpet::Render::HTML, autolink: true, tables: true) %>
 <% @messages.each do |message| %>
   <tr>
     <td>
@@ -8,7 +7,7 @@
   <tr>
     <td style="padding-bottom: 16px;">
       <% if message.content %>
-        <%= markdown.render(message.content).html_safe %>
+        <%= CommonMarker.render_html(message.content).html_safe %>
       <% end %>
       <% if message.attachments %>
         <% message.attachments.each do |attachment| %>