Map END_GATEWAY to END_PORTAL in 1.8->1.9

Closes #150

Author: FlorianMichael

common/src/main/resources/assets/viarewind/data/item-mappings-1.9.json

@@ -115,10 +115,6 @@
       "data": "0",
       "name": "1.9 Grass Path"
     },
-    "209": {
-      "id": "90",
-      "name": "1.9 End Gateway"
-    },
     "210": {
       "id": "137",
       "data": "0",