improved cross-referencing in ppo tutorial

Author: MatteoGaetzner

intermediate_source/reinforcement_ppo.py

@@ -16,7 +16,7 @@
 Key learnings:
 
 - How to create an environment in TorchRL, transform its outputs, and collect data from this environment;
-- How to make your classes talk to each other using :class:`tensordict.TensorDict`;
+- How to make your classes talk to each other using :class:`~tensordict.TensorDict`;
 - The basics of building your training loop with TorchRL:
 
   - How to compute the advantage signal for policy gradient methods;
@@ -690,7 +690,7 @@
 #
 # * From an efficiency perspective,
 #   we could run several simulations in parallel to speed up data collection.
-#   Check :class:`torchrl.envs.ParallelEnv` for further information.
+#   Check :class:`~torchrl.envs.ParallelEnv` for further information.
 #
 # * From a logging perspective, one could add a :class:`torchrl.record.VideoRecorder` transform to
 #   the environment after asking for rendering to get a visual rendering of the