network/dhcp6: do not request IA_PD when running in the other-information mode

network/dhcp6: do not request IA_PD when running in the other-information mode

This reverts the following commits:
- 180cc5421d9712fb95a6bbc725dc8ba459360c8b
  "sd-dhcp6-client: allow to request IA_PD on information requesting mode"
- cf7a403e470368049165ecff7ac7686928778d7c
  "sd-dhcp6-lease: adjust information refresh time with lifetime of IA_PD"
- 1918eda30d12e1ba3ee55921c18ec53267463e24
  "network/dhcp6: process hostname and IA_PD on information requesting mode"

As per discussion in #34299,
https://github.com/systemd/systemd/issues/34299#issuecomment-2425153221
the offending commits violate RFC 8415 section 18.2.6:
> The client uses an Information-request message to obtain
> configuration information without having addresses and/or delegated
> prefixes assigned to it.