Harmonize LDAP "main" server block with documented example

What does this MR do?

1. Our alignment of commented config lines seems off in some cases. A customer reported internally that they stumbled over this one, so I suggest that we indent the commented lines, so that they don't immediately misalign. Ideally, the user's editor should do it, but we can't rely on it.
2. The base: is missing, but documented on https://docs.gitlab.com/charts/charts/globals#ldap

Related issues

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion.

Required

• Merge Request Title and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com

Expected (please provide an explanation if not completing)

• [-] Test plan indicating conditions for success has been posted and passes
• [-] Documentation created/updated
• [-] Tests added
• [-] Integration tests added to GitLab QA
• [-] Equivalent MR/issue for omnibus-gitlab opened

Not needed, because this MR only changes #-commented parts of the config file.