Fix path to /etc/default/gitlab in 8.0 update guide

doc/update/7.14-to-8.0.md

@@ -101,7 +101,7 @@ EOF
 ```
 
 If your Git repositories are in a directory other than `/home/git/repositories`,
-you need to tell `gitlab-git-http-server` about it via `/etc/gitlab/default`.
+you need to tell `gitlab-git-http-server` about it via `/etc/default/gitlab`.
 See `lib/support/init.d/gitlab.default.example` for the options.
 
 ### 6. Copy secrets