Merge pull request #9646 from sameersbn/fix-link-to-docs

fixes link to reply_by_email docs

config/gitlab.yml.example

@@ -96,7 +96,7 @@ production: &base
 
   ## Reply by email
   # Allow users to comment on issues and merge requests by replying to notification emails.
-  # For documentation on how to set this up, see http://doc.gitlab.com/ce/reply_by_email/README.md
+  # For documentation on how to set this up, see http://doc.gitlab.com/ce/reply_by_email/README.html
   reply_by_email:
     enabled: false
     address: "replies+%{reply_key}@gitlab.example.com"