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

data/maps/SlateportCity/map.json

@@ -681,5 +681,12 @@
       "player_facing_dir": "BG_EVENT_PLAYER_FACING_NORTH",
       "script": "SlateportCity_EventScript_BerryCrushRankingsSign"
     }
+  ],
+  "heal_locations": [
+    {
+      "id": "HEAL_LOCATION_SLATEPORT_CITY",
+      "x": 19,
+      "y": 20
+    }
   ]
 }