Move heal locations data to their associated map.json (#2034)

data/maps/PetalburgCity/map.json

@@ -326,5 +326,12 @@
       "item": "ITEM_RARE_CANDY",
       "flag": "FLAG_HIDDEN_ITEM_PETALBURG_CITY_RARE_CANDY"
     }
+  ],
+  "heal_locations": [
+    {
+      "id": "HEAL_LOCATION_PETALBURG_CITY",
+      "x": 20,
+      "y": 17
+    }
   ]
 }