Do not require Kerberos preauthentication - not need to be set

[ra-at-diladele-com]

In the docs we require admin to set this flag - but this is not secure - see https://social.technet.microsoft.com/wiki/contents/articles/23559.kerberos-pre-authentication-why-it-should-not-be-disabled.aspx

We need to clear it in the test lab, re-generate the user and see if the kerberos works ok. If yes - remove this requirement from the docs.

[ra-at-diladele-com]

If we just clear that checkbox - everything runs smoothly.