Fixed ios-bench build

`accessToken` parameter was removed in #1553.

ios/benchmark/MBXBenchViewController.mm

@@ -33,7 +33,7 @@
     [super viewDidLoad];
 
     NSURL* url = [[NSURL alloc] initWithString:@"asset://styles/mapbox-streets-v7.json"];
-    self.mapView = [[MGLMapView alloc] initWithFrame:self.view.bounds accessToken:nil styleURL:url];
+    self.mapView = [[MGLMapView alloc] initWithFrame:self.view.bounds styleURL:url];
     self.mapView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
     self.mapView.delegate = self;
     self.mapView.zoomEnabled = NO;