fix: reward and discount spec not in wrapper

[sash-a]

The reward_spec and discount_spec methods are not in Wrapper. As such when wrapping an environment with a reward/discount spec that is not the default (shape=()), the reward and discount specs are set to the default unless they are specified again in the wrapper.

For example

class MyWrapper(Wrapper):
    def reset(self, key):
        do_some_stuff()
        return self._env.reset(key)

env = Connector()
wrapped = MyWrapper(env)

env.reward_spec() == wrapped.reward_spec()  # <-- false

[clement-bonnet]

Well spotted, thanks!