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

data/maps/MauvilleCity/map.json

@@ -296,5 +296,12 @@
       "player_facing_dir": "BG_EVENT_PLAYER_FACING_ANY",
       "script": "MauvilleCity_EventScript_GameCornerSign"
     }
+  ],
+  "heal_locations": [
+    {
+      "id": "HEAL_LOCATION_MAUVILLE_CITY",
+      "x": 22,
+      "y": 6
+    }
   ]
 }