Update LDAP documentation to make multiple server support clearer
Zendesk issue: https://gitlab.zendesk.com/agent/tickets/13921
Related to #139 (closed)
Update the LDAP documentation to make it clear how multiple LDAP servers work. For example, this is meant for allowing users from multiple directories to sign in to GitLab. This is not meant for failover - because we store identities according to provider name.
cc/ @axil
Edited by Service Account - security-triage