Don't render HTML stripping the tags for comment bodies, use to_plain_text instead

This will prevent error when generating notification bundles such as:

Type	ActionView::Template::Error
Message	undefined method 'rails_blob_path' for an instance of #<Class:0x00007fbb7e0c2a88>

We could just use the _url variant but this feels better nevertheless

app/helpers/notifications_helper.rb

@@ -85,7 +85,7 @@ module NotificationsHelper
 
     def comment_notification_body(event)
       comment = event.eventable
-      strip_tags(comment.body.to_s).truncate(200)
+      comment.body.to_plain_text.truncate(200)
     end
 
     def card_notification_title(card)