Update discrete_act.py (#29)

* Update discrete_act.py

Use list operators
Fix docstring

rlgym/utils/action_parsers/discrete_act.py

@@ -6,7 +6,7 @@
 
 class DiscreteAction(ActionParser):
     """
-        Simple discrete action space. All the analog actions have 3 bins: -1, 0 and 1.
+    Simple discrete action space. All the analog actions have 3 bins by default: -1, 0 and 1.
     """
 
     def __init__(self, n_bins=3):
@@ -15,7 +15,7 @@ def __init__(self, n_bins=3):
         self._n_bins = n_bins
 
     def get_action_space(self) -> gym.spaces.Space:
-        return gym.spaces.MultiDiscrete([self._n_bins, self._n_bins, self._n_bins, self._n_bins, self._n_bins, 2, 2, 2])
+        return gym.spaces.MultiDiscrete([self._n_bins] * 5 + [2] * 3)
 
     def parse_actions(self, actions: np.ndarray, state: GameState) -> np.ndarray:
         actions = actions.reshape((-1, 8))