Doc: Update default recommended memory

Open username-removed-307349 requested to merge webysther/gitlab-ce:patch-23 into master

What does this MR do?

Update the default requirements based on the real and isolated usage. The active users peak is 90 and the memory never stay low than 4GB.

Specs:

  • The server is a dedicated and virtual.
  • Gitlab Runner is running in another 5 bare metal servers with docker-only build.

Are there points in the code the reviewer needs to double check?

No

Screenshots (if relevant)

180

6

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/21791

Edited by username-removed-307349