You deleted the route for 
> /projects/:project_id/issues/calendar

 and added one for
>/work_packages/calendar

There is still a route defined for
>/issues/calendar

while the one for 
> /projects/:project_id/work_packages/calendar

is missing. The test for that route is missing, too.

This results in the url for the calendar menu entry beeing displayed as e.g.
> /work_packages/calendar?project_id=openproject