remove unused reference

include/mbgl/map/map.hpp

@@ -240,8 +240,6 @@ private:
     // Stores whether the map thread has been stopped already.
     std::atomic_bool isStopped;
 
-    FileSource& fileSource;
-
     util::ptr<GlyphStore> glyphStore;
     util::ptr<Style> style;
     util::ptr<Sprite> sprite;

src/mbgl/map/map.cpp

@@ -85,7 +85,6 @@ Map::Map(View& view_, FileSource& fileSource_)
       view(view_),
       data(util::make_unique<MapData>(view_)),
       context(util::make_unique<MapContext>()),
-      fileSource(fileSource_),
       glyphStore(std::make_shared<GlyphStore>(*env)),
       texturePool(std::make_shared<TexturePool>()),
       updated(static_cast<UpdateType>(Update::Nothing))