Merge branch 'cs-upgrade-ruby-docs' into 'master'

Add Ruby 2.3 upgrade notes.

The 8.10 to 8.11 docs didn't mention Ruby 2.3, now they do.

See merge request !5940

doc/update/8.10-to-8.11.md

@@ -65,7 +65,7 @@ For GitLab Enterprise Edition:
 sudo -u git -H git checkout 8-11-stable-ee
 ```
 
-### 4. Update gitlab-shell
+### 5. Update gitlab-shell
 
 ```bash
 cd /home/git/gitlab-shell
@@ -73,7 +73,7 @@ sudo -u git -H git fetch --all --tags
 sudo -u git -H git checkout v3.4.0
 ```
 
-### 5. Update gitlab-workhorse
+### 6. Update gitlab-workhorse
 
 Install and compile gitlab-workhorse. This requires
 [Go 1.5](https://golang.org/dl) which should already be on your system from
@@ -86,7 +86,7 @@ sudo -u git -H git checkout v0.7.8
 sudo -u git -H make
 ```
 
-### 6. Install libs, migrations, etc.
+### 7. Install libs, migrations, etc.
 
 ```bash
 cd /home/git/gitlab
@@ -108,7 +108,7 @@ sudo -u git -H bundle exec rake assets:clean assets:precompile cache:clear RAILS
 
 ```
 
-### 7. Update configuration files
+### 8. Update configuration files
 
 #### New configuration options for `gitlab.yml`
 
@@ -157,12 +157,12 @@ Ensure you're still up-to-date with the latest init script changes:
 
     sudo cp lib/support/init.d/gitlab /etc/init.d/gitlab
 
-### 8. Start application
+### 9. Start application
 
     sudo service gitlab start
     sudo service nginx restart
 
-### 9. Check application status
+### 10. Check application status
 
 Check if GitLab and its environment are configured correctly: