[core] rename backend to renderer backend

test/map/prefetch.test.cpp

@@ -3,9 +3,9 @@
 
 #include <mbgl/gl/headless_backend.hpp>
 #include <mbgl/gl/offscreen_view.hpp>
-#include <mbgl/map/backend_scope.hpp>
 #include <mbgl/map/map.hpp>
 #include <mbgl/renderer/renderer.hpp>
+#include <mbgl/renderer/backend_scope.hpp>
 #include <mbgl/storage/default_file_source.hpp>
 #include <mbgl/style/style.hpp>
 #include <mbgl/util/default_thread_pool.hpp>