Fix: not detecting mentions when publishing saved drafts

The problem was that publishing a card with `#publish` was tracking the event
after updating the status, which was clearing the saved changes and preventing the
code from detecting the mention.

See:
https://app.fizzy.do/5986089/cards/2835

test/models/concerns/mentions_test.rb

@@ -23,7 +23,7 @@ class MentionsTest < ActiveSupport::TestCase
       card = Card.find(card.id)
 
       assert_difference -> { Mention.count }, +1 do
-        card.published!
+        card.publish
       end
     end
   end