Update link to "Configuring LDAP as an ext auth" in Satellite web UI

[asteflova]

          Actually, it looks like I could just update the ID in [foreman_theme_satellite](https://github.com/RedHatSatellite/foreman_theme_satellite/blob/b6ee897d49a8b2d9f8b2589e9105ad5b433e5868/lib/foreman_theme_satellite/documentation.rb#L51).

Let's leave things as they are in this PR, but I'll create an issue for this. The plan would be to update the link in foreman_theme_satellite, and then to remove the secondary ID from guides/common/modules/con_configuring-an-ldap-server-as-an-external-identity-provider-for-project.adoc.

Originally posted by @asteflova in #2975 (comment)