Merge branch 'docs-update_gitlab_workhorse_for_8.11' into 'master'

docs: make sure to update 8.10-to-8.11 workhorse version too (see !5983)

## What does this MR do?

Make sure to remember the correct workhorse version for specific version update instructions for those of us still doing source installs.
Related to !5983.

See merge request !6049

doc/update/8.10-to-8.11.md

@@ -82,7 +82,7 @@ GitLab 8.1.
 ```bash
 cd /home/git/gitlab-workhorse
 sudo -u git -H git fetch --all
-sudo -u git -H git checkout v0.7.8
+sudo -u git -H git checkout v0.7.11
 sudo -u git -H make
 ```