Follow up on dhclient(8) to dhcpleased(8)/resolvd(8) switch

Follow up on dhclient(8) to dhcpleased(8)/resolvd(8) switch

hostname.if(5)'s "dhcp" no longer triggers dhclient in any way, so suggest
the simple "inet autoconf" instead while mentioning "dhcp" as an alias for
that.

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There is more room for improvemen in this manual.

Feedback deraadt, "go ahead"