mapnik 3.0.15 and removing gdal

carto-package.json

@@ -9,8 +9,7 @@
             "redis": ">=3.0.0",
             "postgresql": ">=9.5",
             "postgis": ">=2.2",
-            "mapnik": ">=3.0.12  checking if needed",
-            "gdal":">=2.1.1  checking if needed"
+            "mapnik": ">=3.0.15"
         }
     }
 }