bug#34289: Mention why killed groups come back anyway next time one starts gnus

[積丹尼 Dan Jacobson]

>>>>> "LI" == Lars Ingebrigtsen <larsi@gnus.org> writes:

LI> And if you kill a group, it comes back the next time you start Gnus?
LI> Have you set `gnus-save-killed-list' to nil?

!gnus-save-killed-list is a variable defined in ‘gnus-start.el’.
!Its value is nil
!Original value was t
!You should always set ‘gnus-check-new-newsgroups’ to ‘ask-server’...(yes)