Update gitlab-shell documentation [ci skip]

doc/install/installation.md

@@ -312,7 +312,7 @@ We recommend using a PostgreSQL database. For MySQL check [MySQL setup guide](da
 GitLab Shell is an SSH access and repository management software developed specially for GitLab.
 
     # Run the installation task for gitlab-shell (replace `REDIS_URL` if needed):
-    sudo -u git -H bundle exec rake gitlab:shell:install[v2.6.6] REDIS_URL=unix:/var/run/redis/redis.sock RAILS_ENV=production
+    sudo -u git -H bundle exec rake gitlab:shell:install[v2.6.7] REDIS_URL=unix:/var/run/redis/redis.sock RAILS_ENV=production
 
     # By default, the gitlab-shell config is generated from your main GitLab config.
     # You can review (and modify) the gitlab-shell config as follows:

doc/update/8.1-to-8.2.md

@@ -68,7 +68,7 @@ sudo -u git -H git checkout 8-2-stable-ee
 ```bash
 cd /home/git/gitlab-shell
 sudo -u git -H git fetch
-sudo -u git -H git checkout v2.6.6
+sudo -u git -H git checkout v2.6.7
 ```
 
 ### 5. Replace gitlab-git-http-server with gitlab-workhorse