[Doc] Fix wrong default value for flatten_tensordicts in ReplayBuffer…

…Trainer (#2502)

torchrl/trainers/trainers.py

@@ -633,14 +633,14 @@ class ReplayBufferTrainer(TrainerHookBase):
             the replay buffer batch-size will be used (preferred option for
             unchanged batch-sizes).
         memmap (bool, optional): if ``True``, a memmap tensordict is created.
-            Default is False.
+            Default is ``False``.
         device (device, optional): device where the samples must be placed.
-            Default is cpu.
+            Default is ``cpu``.
         flatten_tensordicts (bool, optional): if ``True``, the tensordicts will be
             flattened (or equivalently masked with the valid mask obtained from
             the collector) before being passed to the replay buffer. Otherwise,
             no transform will be achieved other than padding (see :obj:`max_dims` arg below).
-            Defaults to True
+            Defaults to ``False``.
         max_dims (sequence of int, optional): if :obj:`flatten_tensordicts` is set to False,
             this will be a list of the length of the batch_size of the provided
             tensordicts that represent the maximum size of each. If provided,