[No GBP] Traders use Pick() to select their first customer (#79455)

## About The Pull Request

In my trader PR, I made
`/datum/ai_behavior/find_and_set/conscious_person` return the first
person the trader found, since all they had to know was that they found
someone. However, I realized that I made the jumpscare subtype actually
move towards the target, meaning they would always move to the first
target they found in their vision range. This PR makes them use Pick().

## Why It's Good For The Game

Its good if an AI randomly picks from a search list instead of returning
the first one.

## Changelog

Nothing player facing

code/datums/ai/generic/find_and_set.dm

@@ -142,7 +142,13 @@
 /datum/ai_behavior/find_and_set/conscious_person
 
 /datum/ai_behavior/find_and_set/conscious_person/search_tactic(datum/ai_controller/controller, locate_path, search_range)
+	var/list/customers = list()
 	for(var/mob/living/carbon/human/target in oview(search_range, controller.pawn))
 		if(IS_DEAD_OR_INCAP(target) || !target.mind)
 			continue
-		return target
+		customers += target
+
+	if(customers.len)
+		return pick(customers)
+
+	return null