clarify which configs should be updated

doc/update/7.1-to-7.2.md

@@ -41,7 +41,7 @@ For GitLab Enterprise Edition:
 sudo -u git -H git checkout 7-2-stable-ee
 ```
 
-### 3. Update gitlab-shell (and its config)
+### 3. Update gitlab-shell
 
 ```bash
 cd /home/git/gitlab-shell
@@ -84,12 +84,18 @@ sudo chmod +x /etc/init.d/gitlab
 
 #### New configuration options for gitlab.yml
 
-There are new configuration options available for gitlab.yml. View them with the command below and apply them to your current gitlab.yml if desired.
+There are new configuration options available for gitlab.yml. View them with the command below and apply them to your current gitlab.yml.
 
 ```
 git diff 7-1-stable:config/gitlab.yml.example 7-2-stable:config/gitlab.yml.example
 ```
 
+Update rack attack middleware config
+
+```
+sudo -u git -H cp config/initializers/rack_attack.rb.example config/initializers/rack_attack.rb
+```
+
 ### 7. Start application
 
     sudo service gitlab start