Get rid of boost::optional leftovers (#6977)

include/engine/guidance/assemble_steps.hpp

@@ -17,9 +17,9 @@
 #include "util/guidance/turn_lanes.hpp"
 #include "util/typedefs.hpp"
 
-#include <boost/optional.hpp>
 #include <cstddef>
 #include <guidance/turn_bearing.hpp>
+#include <optional>
 #include <vector>
 
 namespace osrm::engine::guidance

include/engine/guidance/route_leg.hpp

@@ -3,7 +3,7 @@
 
 #include "engine/guidance/route_step.hpp"
 
-#include <boost/optional.hpp>
+#include <optional>
 
 #include <string>
 #include <vector>