[ci skip] Update Gitaly installation documentation

Now the rake task takes the path to the default storage directory.

doc/install/installation.md

@@ -460,11 +460,11 @@ GitLab-Pages uses [GNU Make](https://www.gnu.org/software/make/). This step is o
 ### Install Gitaly
     # Fetch Gitaly source with Git and compile with Go
-    sudo -u git -H bundle exec rake "gitlab:gitaly:install[/home/git/gitaly]" RAILS_ENV=production
+    sudo -u git -H bundle exec rake "gitlab:gitaly:install[/home/git/gitaly,/home/git/repositories]" RAILS_ENV=production
 You can specify a different Git repository by providing it as an extra parameter:
-    sudo -u git -H bundle exec rake "gitlab:gitaly:install[/home/git/gitaly,https://example.com/gitaly.git]" RAILS_ENV=production
+    sudo -u git -H bundle exec rake "gitlab:gitaly:install[/home/git/gitaly,/home/git/repositories,https://example.com/gitaly.git]" RAILS_ENV=production
 Next, make sure gitaly configured:

doc/update/patch_versions.md

@@ -83,7 +83,7 @@ sudo -u git -H bundle exec rake "gitlab:workhorse:install[/home/git/gitlab-workh
 ```bash
 cd /home/git/gitlab
-sudo -u git -H bundle exec rake "gitlab:gitaly:install[/home/git/gitaly]" RAILS_ENV=production
+sudo -u git -H bundle exec rake "gitlab:gitaly:install[/home/git/gitaly,/home/git/repositories]" RAILS_ENV=production
 ```
 ### 6. Update gitlab-shell to the corresponding version