removed get_queryset and overide get method in event_details view

The main part of implementing get queryset is to know that the event object with show=True or False. This is known by implementing a get_queryset in the current implementation which returns events which has show=True. So if for an event, get_queryset is checking that if the particular event is there in the get_queryset or not, If not we are raising a 404 error(as we dont want to display the event with show=False). As it should not be a part of get_queryset i removed it and override the get method to implement the same