Remove linkgraph duration not day length scaled setting

Now always enabled

src/settings_type.h

@@ -712,7 +712,6 @@ struct EconomySettings {
 struct LinkGraphSettings {
 	uint16 recalc_time;                         ///< time (in days) for recalculating each link graph component.
 	uint16 recalc_interval;                     ///< time (in days) between subsequent checks for link graphs to be calculated.
-	bool recalc_not_scaled_by_daylength;        ///< whether the time should be in daylength-scaled days (false) or unscaled days (true)
 	DistributionType distribution_pax;          ///< distribution type for passengers
 	DistributionType distribution_mail;         ///< distribution type for mail
 	DistributionType distribution_armoured;     ///< distribution type for armoured cargo class