Remove V2 world goals

[jwaa]

Is your feature request related to a problem? Please describe.
The V2 world goals (e.g., WorldGoalV2) need to be removed. After being deprecated according to #291

This also includes the adjustments of several lines in GridWorld.__check_simulation_goal, as the check between V2 and regular is not necessary anymore:

if isinstance(self.__simulation_goal, (list, tuple)):  # edited this check to include tuples
    for sim_goal in self.__simulation_goal:

        # Check if the goal is a new V2 goal
        if isinstance(sim_goal, WorldGoalV2):
            is_done = sim_goal.goal_reached(world_state, self)
        else:
            is_done = sim_goal.goal_reached(world_state, self)

        # Store goal status
        goal_status[sim_goal] = is_done
else:
    # Check if the goal is a new V2 goal
    if isinstance(self.__simulation_goal, WorldGoalV2):
        is_done = self.__simulation_goal.goal_reached(world_state, self)
    else:
        is_done = self.__simulation_goal.goal_reached(world_state, self)
    goal_status[self.__simulation_goal] = is_done

Describe the solution you would like
N/A

Describe alternatives you have considered
N/A

Additional context
The last step after #291 to allow for sufficient time to go for MATRX users to adapt to the V2 world goals and then to phase out the V2 back to normal naming.