wifi: iwlwifi: mld: remove support for iwl_mcc_update_resp versions

iwlmld was planned to be used for HR/GF, which has versions 5/6,
but it was decided at the end to use iwlmvm for HR/GF, so iwlmld only
needs to support version 8.
Remove versions 5 and 6 support.

Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250711183056.9c64bfbb16cb.I109bee4d4bf455cbffbb8d2340023338bcab886d@changeid