wifi: iwlwifi: mld: remove unused scan expire time constants

wifi: iwlwifi: mld: remove unused scan expire time constants

Remove the unused IWL_MLD_SCAN_EXPIRE_TIME_SEC constant from
constants.h and its corresponding IWL_MLD_SCAN_EXPIRE_TIME
macro definition from mlo.c. These definitions are no longer
referenced.

Signed-off-by: Pagadala Yesu Anjaneyulu <pagadala.yesu.anjaneyulu@intel.com>
Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20260319110722.4be7221113cf.I13e32d575bb854709af374519332b998bc1fed4a@changeid