Update Unicorn Worker recommendation
Update Unicorn Worker recommendation

Update the Unicorn worker documentation based on the new scaling
formula.

https://gitlab.com/gitlab-org/omnibus-gitlab/issues/4535

mmkassem/gitlabhq,mmkassem/gitlabhq,stoplightio/gitlabhq,stoplightio/gitlabhq,mmkassem/gitlabhq,mmkassem/gitlabhq,stoplightio/gitlabhq,stoplightio/gitlabhq