Remove rotation constraints

This should be an iOS SDK option, not hard coded into
low-level renderering.

Fixes #458

src/map/map.cpp

@@ -551,10 +551,6 @@ void Map::stopRotating() {
     update();
 }
 
-bool Map::canRotate() {
-    return transform.canRotate();
-}
-
 
 #pragma mark - Toggles