Use gitlab-shell 1.9.3

doc/update/6.0-to-6.8.md

@@ -57,7 +57,7 @@ sudo apt-get install logrotate
 ```bash
 cd /home/git/gitlab-shell
 sudo -u git -H git fetch
-sudo -u git -H git checkout v1.9.1 # Addresses multiple critical security vulnerabilities
+sudo -u git -H git checkout v1.9.3 # Addresses multiple critical security vulnerabilities
 ```
 
 ### 5. Install libs, migrations, etc.