Update docs for process_turn in the profile docs (#4786)

* update correct attributes available in process turn

* make travel mode in ExtractedTurn const

* fix mismatch of struct and class

include/extractor/extraction_turn.hpp

@@ -39,8 +39,8 @@ struct ExtractionTurn
     const bool is_left_hand_driving;
     double weight;
     double duration;
-    TravelMode source_mode;
-    TravelMode target_mode;
+    const TravelMode source_mode;
+    const TravelMode target_mode;
 };
 }
 }

include/extractor/guidance/turn_discovery.hpp

@@ -12,7 +12,7 @@ namespace osrm
 {
 namespace util
 {
-class Coordinate;
+struct Coordinate;
 }
 
 namespace extractor