Hotfix to wrong spawn group name related to helicopters (#1141)

Hotfix to wrong spawn group name related to helicopters

Co-authored-by: firestorm01x2 <firestorm01x2gmail.com>

data/json/mapgen/regional_airport.json

@@ -864,7 +864,7 @@
       "F": { "item": "file_room", "chance": 70, "repeat": [ 1, 2 ] },
       "l": { "item": "clothing_work_set", "chance": 70 },
       "r": { "item": "mechanics", "chance": 30, "repeat": [ 1, 2 ] },
-      "k": [ { "item": "mechanics", "chance": 40, "repeat": [ 1, 3 ] }, { "item": "supplies_civilian_helicopter", "chance": 15 } ],
+      "k": [ { "item": "mechanics", "chance": 40, "repeat": [ 1, 3 ] }, { "item": "civilian_helicopter_parts", "chance": 15 } ],
       "D": { "item": "trash", "chance": 70, "repeat": [ 3, 6 ] },
       "O": [
         { "item": "supplies_electronics", "chance": 20, "repeat": [ 1, 2 ] },