Remove TODO comments

Most of the other concept exercises up to this one communicate the requirement to implement the functions by using docstrings and `pass`, so I think it makes sense to be consistent and do it here as well.

Author: ceddlyburge

exercises/concept/locomotive-engineer/locomotive_engineer.py

@@ -1,7 +1,6 @@
 """Functions which helps the locomotive engineer to keep track of the train."""
 
 
-# TODO: define the 'get_list_of_wagons' function
 def get_list_of_wagons():
     """Return a list of wagons.
 
@@ -11,7 +10,6 @@ def get_list_of_wagons():
     pass
 
 
-# TODO: define the 'fixListOfWagons()' function
 def fix_list_of_wagons(each_wagons_id, missing_wagons):
     """Fix the list of wagons.
 
@@ -22,7 +20,6 @@ def fix_list_of_wagons(each_wagons_id, missing_wagons):
     pass
 
 
-# TODO: define the 'add_missing_stops()' function
 def add_missing_stops():
     """Add missing stops to route dict.
 
@@ -33,7 +30,6 @@ def add_missing_stops():
     pass
 
 
-# TODO: define the 'extend_route_information()' function
 def extend_route_information(route, more_route_information):
     """Extend route information with more_route_information.
 
@@ -44,7 +40,6 @@ def extend_route_information(route, more_route_information):
     pass
 
 
-# TODO: define the 'fix_wagon_depot()' function
 def fix_wagon_depot(wagons_rows):
     """Fix the list of rows of wagons.