Correct branches for CE to EE guides

Several of these had the user going back to the `-ee` version of the
stable branch in the "Things went south?" section, when really they
should be reverting to the CE version.

One had the wrong version entirely.

doc/update/11.5-ce-to-ee.md

@@ -77,13 +77,13 @@ sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production
 
 If all items are green, then congratulations upgrade complete!
 
-## Things went south? Revert to previous version (Community Edition 11.4)
+## Things went south? Revert to previous version (Community Edition 11.5)
 
 ### 1. Revert the code to the previous version
 
 ```bash
 cd /home/git/gitlab
-sudo -u git -H git checkout 11-4-stable-ee
+sudo -u git -H git checkout 11-5-stable
 ```
 
 ### 2. Restore from the backup

doc/update/11.6-ce-to-ee.md

@@ -83,7 +83,7 @@ If all items are green, then congratulations upgrade complete!
 
 ```bash
 cd /home/git/gitlab
-sudo -u git -H git checkout 11-6-stable-ee
+sudo -u git -H git checkout 11-6-stable
 ```
 
 ### 2. Restore from the backup

doc/update/11.7-ce-to-ee.md

@@ -83,7 +83,7 @@ If all items are green, then congratulations upgrade complete!
 
 ```bash
 cd /home/git/gitlab
-sudo -u git -H git checkout 11-7-stable-ee
+sudo -u git -H git checkout 11-7-stable
 ```
 
 ### 2. Restore from the backup